new research on muscle growth

May 25, 2021

New study shows how to boost muscle regeneration and rebuild tissue

Salk research reveals clues about molecular changes underlying muscle loss tied to aging

Home - Salk News - New study shows how to boost muscle regeneration and rebuild tissue

LA JOLLA—One of the many effects of aging is loss of muscle mass, which contributes to disability in older people. To counter this loss, scientists at the Salk Institute are studying ways to accelerate the regeneration of muscle tissue, using a combination of molecular compounds that are commonly used in stem-cell research.

In a study published on May 25, 2021, in Nature Communications , the investigators showed that using these compounds increased the regeneration of muscle cells in mice by activating the precursors of muscle cells, called myogenic progenitors. Although more work is needed before this approach can be applied in humans, the research provides insight into the underlying mechanisms related to muscle regeneration and growth and could one day help athletes as well as aging adults regenerate tissue more effectively.

“Loss of these progenitors has been connected to age-related muscle degeneration,” says Salk Professor Juan Carlos Izpisua Belmonte , the paper’s senior author. “Our study uncovers specific factors that are able to accelerate muscle regeneration, as well as revealing the mechanism by which this occurred.”

The compounds used in the study are often called Yamanaka factors after the Japanese scientist who discovered them. Yamanaka factors are a combination of proteins (called transcription factors) that control how DNA is copied for translation into other proteins. In lab research, they are used to convert specialized cells, like skin cells, into more stem-cell-like cells that are pluripotent, which means they have the ability to become many different types of cells.

“Our laboratory previously showed that these factors can rejuvenate cells and promote tissue regeneration in live animals,” says first author Chao Wang, a postdoctoral fellow in the Izpisua Belmonte lab. “But how this happens was not previously known.”

Muscle regeneration is mediated by muscle stem cells, also called satellite cells. Satellite cells are located in a niche between a layer of connective tissue (basal lamina) and muscle fibers (myofibers). In this study, the team used two different mouse models to pinpoint the muscle stem-cell-specific or niche-specific changes following addition of Yamanaka factors. They focused on younger mice to study the effects of the factors independent of age.

In the myofiber-specific model, they found that adding the Yamanaka factors accelerated muscle regeneration in mice by reducing the levels of a protein called Wnt4 in the niche, which in turn activated the satellite cells. By contrast, in the satellite-cell-specific model, Yamanaka factors did not activate satellite cells and did not improve muscle regeneration, suggesting that Wnt4 plays a vital role in muscle regeneration.

According to Izpisua Belmonte, who holds the Roger Guillemin Chair, the observations from this study could eventually lead to new treatments by targeting Wnt4.

“Our laboratory has recently developed novel gene-editing technologies that could be used to accelerate muscle recovery after injury and improve muscle function,” he says. “We could potentially use this technology to either directly reduce Wnt4 levels in skeletal muscle or to block the communication between Wnt4 and muscle stem cells.”

The investigators are also studying other ways to rejuvenate cells, including using mRNA and genetic engineering. These techniques could eventually lead to new approaches to boost tissue and organ regeneration.

Other authors included: Ruben Rabadan Ros, Paloma Martinez Redondo, Zaijun Ma, Lei Shi, Yuan Xue, Isabel Guillen-Guillen, Ling Huang, Tomoaki Hishida, Hsin-Kai Liao, Concepcion Rodriguez Esteban, and Pradeep Reddy of Salk; Estrella Nuñez Delicado of Universidad Católica San Antonio de Murcia in Spain; and Pedro Guillen Garcia of Clinica CEMTRO in Spain.

The work was funded by NIH-NCI CCSG: P30 014195, the Helmsley Trust, Fundacion Ramon Areces, Asociación de Futbolistas Españoles (AFE), Fundacion Pedro Guillen, Universidad Católica San Antonio de Murcia (UCAM), the Moxie Foundation and CIRM (GC1R-06673-B).

DOI: 10.1038/s41467-021-23353-z

PUBLICATION INFORMATION

Nature Communications

In vivo partial reprogramming of myofibers promotes muscle regeneration by remodeling the stem cell niche

Chao Wang, Ruben Rabadan Ros, Paloma Martinez Redondo, Zaijun Ma, Lei Shi, Yuan Xue, Isabel Guillen-Guillen, Ling Huang, Tomoaki Hishida, Hsin-Kai Liao, Estrella Nuñez Delicado, Concepcion Rodriguez Esteban, Pedro Guillen Garcia, Pradeep Reddy and Juan Carlos Izpisua Belmonte

Healthy Aging

For more information.

Office of Communications Tel: (858) 453-4100 [email protected]

The Salk Institute For Biological Studies:

Unlocking the secrets of life itself is the driving force behind the Salk Institute. Our team of world-class, award-winning scientists pushes the boundaries of knowledge in areas such as neuroscience, cancer research, aging, immunobiology, plant biology, computational biology and more. Founded by Jonas Salk, developer of the first safe and effective polio vaccine, the Institute is an independent, nonprofit research organization and architectural landmark: small by choice, intimate by nature, and fearless in the face of any challenge.

Connect With Us

Keep in touch.

Inside Salk

Explore our magazine.

Every cure begins with you.

Latest discoveries, events & more.

Your partnership allows our scientists to accelerate the pace of high-risk, high-reward discoveries that have the potential to benefit the health of all humanity-be it cancer, Alzheimer’s disease, climate change, infectious diseases or more.

• Skip to primary navigation
• Skip to main content
• Skip to primary sidebar

The Online Home for Strength Sports

These Researchers Reveal the Right Way to Train for More Muscle Mass

Here are mass-building recommendations published in the international journal of strength and conditioning..

When it comes to gaining muscle , everything your local gym bro told you is right. Ok, that’s not entirely true , but a position paper from the International Universities Strength and Conditioning Association (IUSCA), published in the International Journal of Strength and Conditioning , states that a handful of tried-and-and true practices may be the right way to approach hypertrophy training . 

The main takeaways? Each week, you need to hit each muscle with at least 10 intense sets, taken to near-failure. You should work in the six to 12 rep range most often. It’s important to work the muscle from various angles and rest between one to two minutes per set. Oh, and frequency — meaning how often you train — is less important than the total volume. ( 1 )

The position paper was authored by a team of eight “leading experts in the field,” including Associate Professor of Exercise at Lehman College Brad Schoenfeld , Ph.D. The paper contains the IUSCA’s evidence-based recommendations on how best to induce hypertrophy in an athletic population . The paper is 30-pages long and includes 248 citations. 

Here’s a more in-depth breakdown of the actual findings published on August 16, 2021.

IUSCA Consensus Recommendation Variables

Rest interval, exercise selection, set end point.

            View this post on Instagram                         A post shared by IUSCA (@iusca__)

[Related: The Ultimate Guide to Building Your Own Bodybuilding Workout Plan ] 

A Breakdown of How to Build Muscle Mass, According to the IUSCA

Below is a more in-depth review of the consensus recommendations for each of the six training factors for muscle hypertrophy .

When it comes to how much load to use per set, muscle hypertrophy can be achieved “across a wide spectrum of loading zones.” A moderate rep range — six to 12 — may be preferred since it’s more time-efficient than higher-rep sets and less strenuous on the body than heavy, low-rep sets.  

The researchers conclude that training multiple rep ranges still may be the best for hypertrophy. You can vary rep ranges set to set — so one set of 15 reps, followed by a set of 10 reps, followed by a heavy set of five reps. Or, the researchers suggest focusing on specific rep ranges in different training blocks — four weeks of low reps, four weeks of moderate reps, and four weeks of high reps. 

What it means for you:  Don’t spend too much time trying to lift heavy if you don’t want to. You should lift loads that are difficult to complete but not so hard that you can’t accumulate the recommended six to 12 reps per set . You can (and probably should) vary your rep ranges within a session from “set to set” or by implementing different training blocks that focus on a specific rep range. 

Generally speaking, evidence suggests that at least 10 sets per muscle per week is the ideal number to induce hypertrophy . Not everyone will need that many sets, and some may need more, but 10 sets per muscle per week is the baseline to adjust from.

For underdeveloped muscle groups, more volume will potentially lead to more hypertrophic benefits. If your biceps are lagging, then feel free to add a few more sets to your weekly program. You should increase a body part’s volume by a maximum of 20 percent week over week. If you perform 10 sets of biceps curls during week one of your program, for example, add no more than two sets of volume to the next week of training. 

What it means for you:  Aim for 10 sets per muscle group per week. You can divvy up those sets however you like. For those who enjoy following the “back and bis” or the “ chest and tris ” workout splits , do what works best for your schedule and recovery needs . You can perform all 10 sets for a muscle group in a single session or do those 10 sets over the course of multiple sessions — get the sets done each week . 

This may be, for many, the most surprising finding in the paper: Hypertrophic results are not reliant on training frequency . Evidence suggests that training a muscle group multiple times per week versus a single time per week has the same muscle-building effects, as long as the overall volume is the same. 

The researchers say that it may be “advantageous” to spread out volume over more frequent training sessions. If you’re an advanced trainee who performs more than 10 sets per muscle per week, you may want to divide that volume up between two (or even three) training sessions. 

What it means for you: Organize your workout split however you want. If you prefer to follow a push/pull/legs split , go for it. If you’re going to train your full body twice per week, do it. Or, if you prefer to adhere to a bodybuilding-inspired body part split , then that’s ok, too. The point is, that you want to focus on hitting 10 quality sets per muscle per week. How you serve those sets up is entirely up to you. 

As long as you reach the requisite volume, the gains will come. If you’re opting for more volume, it may be best to spread it out over a few training sessions , the IUSCA says. Ten sets per muscle per session is an appropriate cap. 

The rest interval refers to the amount of rest taken between sets . When performing multi-joint exercises — any exercise that engages multiple joints .groups simultaneously (e.g., back squat ) — you should rest for at least two minutes. For single-joint (read: isolation) exercises, rest for between a minute and 90 seconds.

What it means for you:  You don’t want to be that guy or gal in the gym scrolling through their phone for 10 minutes between sets. That said, you should take a minute to two to rest between sets. Failing to rest between sets could impede the number of reps you would otherwise be able to perform if you lifted to near failure in the previous set (which you should do).

Allow yourself adequate rest between sets, but be mindful to not linger for too long or get lazy. It may help to think of rest intervals as a part of the set and not a break from it.

If you like variety in your training, you’re in luck. The research suggests you should “ include a variety of exercises that work muscles in different planes and angles to ensure complete stimulation of the musculature .” That means divvying up the 10 sets of weekly volume between various exercises is better than performing a single movement for all of them. For example, when training chest, doing incline bench press , decline bench press , cable flyes , and dumbbell flyes is better, the IUSCA says, than solely performing the bench press .

When choosing which exercises to do, include multi-joint and single-joint exercises , enabling “whole muscle development.” Whenever possible, it is recommended to establish a full range of motion for each rep. It’s harder to maintain proper form as you fatigue. Once your form breaks down, you’ve most likely reached failure (or close to it). 

It’s also suggested that free weights reinforce motor skills and coordination compared to machines with a fixed path. 

What it means for you: Have plenty of variety in your program. Choose exercises — both multi- and single-joint — that work your muscles from different angles , as the research shows this does elicit a hypertrophic response. Also, this means that you shouldn’t feel married to a specific exercise. If you want to build a bigger back, but don’t feel the muscles work during deadlifts, don’t do deadlifts. Find exercises that engage the muscle you’re trying to target and stick with them (at least for a few weeks so you can progress a bit). 

The body of research investigated in this paper was too varied in application and diverse for researchers to conclude on set endpoint (which is a different way of saying failure). However, they note that beginners “can achieve robust gains in muscle mass without training at a close proximity to failure.” Comparatively, as a lifter becomes more seasoned in the gym, it is increasingly important to up the intensity . Researchers don’t suggest reaching failure until the final set of each exercise.   

Say you’re working in the six to 12 rep range; you can perform the first couple of sets near with one to two reps left in the tank. Then, on your last set, perform as many reps as needed until you can no longer do the exercise with good form. 

The researchers also say that it may be best to take single-joint or machine exercises to failure to “reduce potential negative consequences on recuperation.”

What it means for you: Be honest with how much you can lift. The goal is to build muscle, not ego. Keep the intensity high and push yourself to near-failure. For most sets, aim to finish with one to two reps left in the tank. We suggest picking a movement or two to take to absolute muscle failure each session. 

In addition, know your recovery plan . How intensely you train in the gym is likely to be a result of how well you recover. If you intend to go hard for a training session, allocate adequate time to recover from it. Having a plan can pay dividends towards staying consistent in the long term.

The Final Word

First, please note that these rules apply to hypertrophy training . If you’re a strength athlete — Olympic weightlifter, Strongman, or Powerlifter — these recommendations aren’t meant to help you gain strength . That’s not to say those athletes can’t benefit from hypertrophy training . Conversely, physique-focused lifters can (and maybe should) take a training block or two to focus on strength (aka lower reps, as the research says). That strength, after all, means more weight on the bar. And more weight on the bar means a better ability to move more weight in a muscle-building rep range. 

You shouldn’t let these recommendations send you into a programming spiral. A lot of this advice — rest one to two minutes between sets, work in the six to 12 rep range, and attack a muscle from different angles — isn’t novel. The news here is that those methods now have the official stamp of approval from a pretty reputable organization.

Can other rep ranges work for growth? Yes (in fact, the paper says so). Is it ok to rest for 45 seconds or three minutes between sets? Sure. Will you morph into a string bean if you miss the recommended 10-set weekly quota? No. 

If you’re looking to start a muscle-building program , the recommendations above are a good starting point. The position paper provides foundational rules for hypertrophy training — but you don’t need to train within a box. 

• Schoenfeld, B., Fisher, J., Grgic, J., Haun, C., Helms, E., Phillips, S., Steele, J., & Vigotsky, A. (2021). Resistance Training Recommendations to Maximize Muscle Hypertrophy in an Athletic Population: Position Stand of the IUSCA.  International Journal of Strength and Conditioning ,  1 (1). https://doi.org/10.47206/ijsc.v1i1.81

Featured image: ALL best fitness is HERE/Shutterstock

About Phil Blechman

Phil is a native New Yorker passionate about storytelling, bodybuilding, and game design. He holds a BFA from Syracuse University.

View All Articles

BarBend is an independent website. The views expressed on this site may come from individual contributors and do not necessarily reflect the view of BarBend or any other organization. BarBend is the Official Media Partner of USA Weightlifting.

• svg]:stroke-accent-900">

This protein may hold one of the secrets to predicting muscle growth

By Sara Chodosh

Posted on Aug 23, 2021 4:21 PM EDT

Muscle building is actually a bit of a mystery. Unsplash

Exercise builds muscle—we just don’t really know why. It might seem like a simple thing, but despite countless articles on how to build muscle ( PopSci included), actual proven research on the cellular mechanisms leading to muscle growth is pretty rare. 

A new study from the University of Cambridge has started to unravel the mystery, though. 

Muscle is generally thought to be borne from stress. When you put strain on your body, it responds by building itself back stronger. But rather than generic stress, the researchers found that at least one of the key signals to grow more muscle comes from an enormous protein called titin.

Titin wraps around the myosin filaments that compose individual muscle fibers, and when muscle fibers contract, a part of titin becomes exposed that’s otherwise inaccessible. That newly exposed site can bind a molecule called phosphate, and when that happens there are a whole slew of other biochemical changes that get triggered—chief among them are signals to synthesize new proteins to build more muscle. 

The idea, then, is pretty simple: the more time a muscle is contracting for or the harder it’s working, the more likely it is that titin molecules have this key binding site exposed. And the longer it’s exposed, the more these muscle-building signaling pathways will get triggered. 

[Related: Everything you’ve ever wanted to know about muscles ]

These researchers constructed a mathematical model to figure out which variables would contribute to muscle growth in an effort to predict muscle growth. They used prior studies on the topic to validate the model, and added in information not just on titin, but also on repetition length, recovery time, and cellular metabolism.

They found that there was actually a level of potentially optimal muscle growth. “While there is experimental data showing similar muscle growth with loads as little as 30 percent of maximum load, our model suggests that loads of 70 percent are a more efficient method of stimulating growth,” said Eugene Terentjev, one of the study authors, in a statement . With too low a load, titin didn’t get activated enough; but too high, muscles were too exhausted to signal properly. 

Their ultimate goal is to create a personalized version that would account for differences between individuals, so that in theory you could enter some information about yourself and get recommendations specific to you. There’s likely a long way to go before that kind of prediction is widely available, but for now it’s simply an improvement to know a bit more about how our muscles operate. Given how crucial exercise is for good health, we know shockingly little about it—and this study gets us a little bit farther.

Latest in Fitness & Exercise

Gertrude ederle and the grueling science of marathon swimming gertrude ederle and the grueling science of marathon swimming.

By Laura Baisas

Roll the tape: What KT Tape taught me about muscles, magnesium, and my limitations Roll the tape: What KT Tape taught me about muscles, magnesium, and my limitations

By Tony Ware

Cellular interplay in skeletal muscle regeneration and wasting: insights from animal models

Affiliations.

• 1 Centre de Recherche Cardio-thoracique de Bordeaux, Univ-Bordeaux, Pessac, France.
• 2 Centre de Recherche Cardio-thoracique de Bordeaux, INSERM, Pessac, France.
• 3 CHU de Bordeaux, Service d'exploration fonctionnelle respiratoire, Pessac, France.
• 4 PhyMedExp, INSERM-CNRS-Montpellier University, Montpellier, France.
• 5 PhyMedExp, INSERM-CNRS-Montpellier University, CHRU Montpellier, Montpellier, France.
• PMID: 36811134
• PMCID: PMC10067506
• DOI: 10.1002/jcsm.13103

Skeletal muscle wasting, whether related to physiological ageing, muscle disuse or to an underlying chronic disease, is a key determinant to quality of life and mortality. However, cellular basis responsible for increased catabolism in myocytes often remains unclear. Although myocytes represent the vast majority of skeletal muscle cellular population, they are surrounded by numerous cells with various functions. Animal models, mostly rodents, can help to decipher the mechanisms behind this highly dynamic process, by allowing access to every muscle as well as time-course studies. Satellite cells (SCs) play a crucial role in muscle regeneration, within a niche also composed of fibroblasts and vascular and immune cells. Their proliferation and differentiation is altered in several models of muscle wasting such as cancer, chronic kidney disease or chronic obstructive pulmonary disease (COPD). Fibro-adipogenic progenitor cells are also responsible for functional muscle growth and repair and are associated in disease to muscle fibrosis such as in chronic kidney disease. Other cells have recently proven to have direct myogenic potential, such as pericytes. Outside their role in angiogenesis, endothelial cells and pericytes also participate to healthy muscle homoeostasis by promoting SC pool maintenance (so-called myogenesis-angiogenesis coupling). Their role in chronic diseases muscle wasting has been less studied. Immune cells are pivotal for muscle repair after injury: Macrophages undergo a transition from the M1 to the M2 state along with the transition between the inflammatory and resolutive phase of muscle repair. T regulatory lymphocytes promote and regulate this transition and are also able to activate SC proliferation and differentiation. Neural cells such as terminal Schwann cells, motor neurons and kranocytes are notably implicated in age-related sarcopenia. Last, newly identified cells in skeletal muscle, such as telocytes or interstitial tenocytes could play a role in tissular homoeostasis. We also put a special focus on cellular alterations occurring in COPD, a chronic and highly prevalent respiratory disease mainly linked to tobacco smoke exposure, where muscle wasting is strongly associated with increased mortality, and discuss the pros and cons of animal models versus human studies in this context. Finally, we discuss resident cells metabolism and present future promising leads for research, including the use of muscle organoids.

Keywords: Cachexia; Fibrocytes; Myofibres; Neutrophils; Sarcopenia.

© 2022 The Authors. Journal of Cachexia, Sarcopenia and Muscle published by John Wiley & Sons Ltd on behalf of Society on Sarcopenia, Cachexia and Wasting Disorders.

Publication types

• Cachexia / pathology
• Endothelial Cells
• Models, Animal
• Muscle, Skeletal / pathology
• Muscular Atrophy / pathology
• Pulmonary Disease, Chronic Obstructive* / pathology
• Quality of Life
• Regeneration* / physiology

• June 3, 2024 | Metabolic Manipulators: How Parasitic Archaea Transform Their Hosts From the Inside Out
• June 3, 2024 | Revolutionizing Neuroscience: Stanford AI Mirrors Brain Organization
• June 3, 2024 | Mapping Earth’s Waterways From Space: How SWOT Transforms Flood Forecasting
• June 3, 2024 | When Aliens Attack: Experts Warn of Urgent Threat to Global Ecosystems
• June 3, 2024 | Scientists Identify 8 Lifestyle Factors That Can Slow Biological Aging

Muscle News

Health May 6, 2024

Unlocking Longevity: New Study Reveals Brain-Muscle Clock Synchronization Prevents Aging

A recent study in mice has revealed that molecular circadian clocks in the brain and muscle tissue work together to maintain muscle health and daily…

Health April 20, 2024

Revolutionary Study Reveals Why Our Muscles Weaken With Age

The first detailed cell atlas of aging human muscle uncovers the complex genetic and cellular activities involved in muscle degeneration and identifies ways to mitigate…

Health March 23, 2024

Natural Ingredient Found in Coffee Could Keep Your Muscles Young

A research consortium led by Nestlé Research in Switzerland and the Yong Loo Lin School of Medicine, National University of Singapore (NUS Medicine) made a…

Health March 1, 2024

Surprising Diet Change Boosts Muscle Strength and Slows Aging

NIH study suggests a small reduction in daily calories is beneficial for wellness. Reducing overall calorie intake may rejuvenate your muscles and activate biological pathways…

Health January 27, 2024

Neck Inflammation: The Hidden Culprit Behind Common Headaches

Researchers presenting at the annual meeting of the Radiological Society of North America (RSNA) have discovered objective evidence showing the involvement of neck muscles in…

Technology January 26, 2024

Scientists Develop Artificial Muscle Device That Produces Force 34 Times Its Weight

Soft robots, medical devices, and wearable devices are now common in our daily routines. Researchers at KAIST have created a fluid switch that employs ionic…

Health January 20, 2024

Meat vs. Plant: New Research Reveals a Clear Winner for Muscle Growth

Evidence contributes to the expanding body of research that indicates protein food sources are essential for building and maintaining muscle. Extensive studies have demonstrated that…

Science December 12, 2023

Melodic Muscles: The Impact of Daily Singing on Songbird Attractiveness

Research on songbirds demonstrates the critical need for daily singing to maintain vocal muscle strength and attractiveness, with implications for human vocal training and speech…

Biology November 14, 2023

Muscle Mat Magic: MIT Engineers a Hydrogel Gym for Cellular Fitness

The vibrating platform could be useful for growing artificial muscles to power soft robots and testing therapies for neuromuscular diseases. There’s no doubt that exercise…

Health November 9, 2023

A New Frontier in Pediatric Care: AI-Driven Growth Charts for Muscle Mass

An analysis of MRI scans led by Brigham researchers using artificial intelligence resulted in the production of a reference growth standard and a fast, reproducible…

Biology October 30, 2023

Scientists Shed New Light on How Endurance Training Transforms Your Muscles

The more we exercise our endurance, the fitter we become – and so do our muscles. They adapt to the load and are able to…

Health October 2, 2023

The Magic Number – New Research Sheds Light on How Often You Need To Exercise To Make It Worth It

A recent study provides insight into the frequency of exercise necessary to reap its benefits. Interested in the health advantages of exercise but not eager…

Health September 23, 2023

Muscling Through “Runner’s Knee” Myths: New Research Sheds Light on Chronic Knee Pain

The new study finds personalized rehabilitation may be needed to effectively address chronic knee pain. Neal Glaviano, assistant professor of kinesiology in the University of…

Health September 17, 2023

Researchers Discover Surprising Side Effect of Common Diabetes Drug

Diabetes might not be the first thing that comes to mind when considering muscle function. However, a widely used diabetes drug that controls blood sugar…

Health September 7, 2023

New Research: High Levels of Lean Muscle Might Protect Against Alzheimer’s Disease

Additional research is required to elucidate the potential biological pathways, according to the authors of the study. High levels of lean muscle could protect against…

Health August 18, 2023

Unmasking the Long COVID Mystery: New Study Reveals Cause of Muscle Weakness

New research paves the way for new strategies to address long-term COVID-19 complications. Researchers from the University of Malta have identified a possible cause for…

Biology August 17, 2023

Lab-Grown Muscles Breakthrough: The Future of Medicine and Meat

Professor Ori Bar-Nur and his colleagues at ETH Zurich are pioneering the cultivation of muscle cells in the lab, currently using mouse cells as their…

Science August 2, 2023

Big Paws, Bigger Problems: Why You Shouldn’t Declaw Tigers or Other Big Cats

A study shows that declawing significantly impacts the muscular capabilities of large cat species more than smaller cats. Despite it being illegal to surgically modify…

Study identifies molecule that stimulates muscle-building in humans

In a randomized control study of 10 healthy young men, researchers compared how consuming the single amino acid leucine or its two-molecule equivalent, dileucine, influenced muscle-building and breakdown. They found that dileucine boosts the metabolic processes that drive muscle growth 42% more than free leucine does.

They report their findings in the Journal of Applied Physiology .

Leucine, isoleucine and valine all are branched-chain amino acids, famous among body builders and health enthusiasts for their purported muscle-enhancing benefits. Like other amino acids, they are the building blocks of proteins. But leucine also acts as a signaling molecule that triggers muscle-building pathways in cells, said University of Illinois Urbana-Champaign kinesiology and community health professor Nicholas Burd, who led the new research with kinesiology graduate student Kevin Paulussen.

Digestion breaks the chemical bonds between the amino acids that make up proteins, resulting in a stew of shorter molecules, including free amino acids and dipeptides. Previous studies have suggested that the small intestine absorbs dipeptides like dileucine more rapidly than their single-molecule counterparts, Burd said.

"But few studies have examined whether dileucine in the diet makes it into the blood as a dipeptide or is first broken down into two leucine molecules," he said. "And no studies have examined its effects on acute muscle-building and breakdown." Burd's laboratory is one of a small number of research facilities set up to study muscle protein metabolism in human participants.

For the new study, participants came to the lab after a 12-hour fast and were infused with stable isotopes, chemical probes that allow researchers to track the process of muscle protein synthesis and breakdown in their muscles. Then biopsies of muscle tissue were taken from the upper leg.

"After that, we fed them either 2 grams of leucine or 2 grams of dileucine," Burd said. "And we studied their muscle-remodeling response for three hours." This was a double-blind study, meaning that the data were coded to prevent participants and researchers from knowing who received leucine or dileucine in the initial phases of the study. Three more muscle biopsies were taken, at 30, 60 and 180 minutes after participants ingested the leucine or dileucine.

"We found that leucine got into the blood more quickly when participants consumed dileucine than if they had just free leucine," Burd said. "That means that some of that dileucine is getting hydrolyzed, or cut up, before it gets into the bloodstream. But we also saw that dileucine was getting into the bloodstream intact."

The next question was whether dileucine had any effect on muscle-building processes, he said.

"So, we looked at pathways that signal the muscle-building process, including protein breakdown as part of the remodeling process. And we found no difference in protein breakdown between the leucine alone and the dileucine condition," Burd said. "But on the protein synthesis side, we saw that dileucine turns up the muscle-building process more than leucine does."

Those who consumed dileucine had 42% more synthesis of new muscle proteins than those who ingested only leucine.

"To put that in perspective, exercise alone can cause a 100-150% increase in the muscle-building response," Burd said.

The researchers also showed that animal-based proteins are the best source of dileucine in the diet. But Burd does not think people should start ingesting large amounts of animal protein or taking dileucine supplements to enhance their muscle metabolism. The study is only a first step toward understanding how the body uses dipeptides, "and focusing on a single nutrient doesn't provide a perspective on how the overall diet and eating pattern impacts muscle growth," he said.

"We don't yet know the mechanism by which dileucine works," Burd said. "This is just a first attempt to understand how these types of peptides are playing a role in human physiology."

• Fibromyalgia
• Dietary Supplements and Minerals
• Chronic Fatigue Syndrome
• Muscular Dystrophy
• Glutamic acid
• Protein biosynthesis
• Motor neuron

Story Source:

Materials provided by University of Illinois at Urbana-Champaign, News Bureau . Original written by Diana Yates. Note: Content may be edited for style and length.

Journal Reference :

• Kevin J. M. Paulussen, Rafael A. Alamilla, Amadeo F. Salvador, Colleen F. McKenna, Andrew T. Askow, Hsin-Yu Fang, Zhong Li, Alexander V. Ulanov, Scott A. Paluska, John A. Rathmacher, Ralf Jäger, Martin Purpura, Nicholas A. Burd. Dileucine ingestion is more effective than leucine in stimulating muscle protein turnover in young males: a double blind randomized controlled trial . Journal of Applied Physiology , 2021; DOI: 10.1152/japplphysiol.00295.2021

Cite This Page :

Explore More

• How Statin Therapy May Prevent Cancer
• Origins of 'Welsh Dragons' Exposed
• Resting Brain: Neurons Rehearse for Future
• Observing Single Molecules
• A Greener, More Effective Way to Kill Termites
• One Bright Spot Among Melting Glaciers
• Martian Meteorites Inform Red Planet's Structure
• Volcanic Events On Jupiter's Moon Io: High Res
• What Negative Adjectives Mean to Your Brain
• 'Living Bioelectronics' Can Sense and Heal Skin

Trending Topics

Strange & offbeat.

• Alzheimer's disease & dementia
• Arthritis & Rheumatism
• Attention deficit disorders
• Autism spectrum disorders
• Biomedical technology
• Diseases, Conditions, Syndromes
• Endocrinology & Metabolism
• Gastroenterology
• Gerontology & Geriatrics
• Health informatics
• Inflammatory disorders
• Medical economics
• Medical research
• Medications
• Neuroscience
• Obstetrics & gynaecology
• Oncology & Cancer
• Ophthalmology
• Overweight & Obesity
• Parkinson's & Movement disorders
• Psychology & Psychiatry
• Radiology & Imaging
• Sleep disorders
• Sports medicine & Kinesiology
• Vaccination
• Breast cancer
• Cardiovascular disease
• Chronic obstructive pulmonary disease
• Colon cancer
• Coronary artery disease
• Heart attack
• Heart disease
• High blood pressure
• Kidney disease
• Lung cancer
• Multiple sclerosis
• Myocardial infarction
• Ovarian cancer
• Post traumatic stress disorder
• Rheumatoid arthritis
• Schizophrenia
• Skin cancer
• Type 2 diabetes
• Full List »

share this!

June 3, 2024

This article has been reviewed according to Science X's editorial process and policies . Editors have highlighted the following attributes while ensuring the content's credibility:

fact-checked

trusted source

New study highlights risks of muscle-building supplement use among adolescents and young adults

by University of Toronto

A recent study from the University of Toronto has revealed critical insights into the use of muscle-building supplements (such as whey protein and creatine) among adolescents and young adults in Canada. The research, published today, provides a comprehensive analysis of the prevalence, influences, and associated risks of muscle-building supplement use, highlighting important implications for health care, public health, and policy-making professionals.

The work is published in the journal Performance Enhancement & Health .

Analyzing data of 912 participants from the Canadian Study of Adolescent Health Behaviors, a national study focused on the mental, social, and behavioral health of individuals 16 to 30 years old found that close to 60% of the respondents reported using protein bars and just over half reported using whey protein powders or protein shakes, which were the most commonly used muscle-building supplement . Boys and men reported higher usage rates compared to girls, women, and transgender/gender expansive (TGE) participants.

"The boys and men in our study reported using an average of three muscle-building supplements in the past 12 months," says Kyle T. Ganson, Ph.D., MSW, the lead author on the study. "This figure truly exemplifies the pervasiveness of boys and men attempting to adhere to the muscular body ideal."

Nearly half of the participants cited social media influencers as the primary influence on their supplement use, while fitness communities and friends also played significant roles. Over two-thirds of the participants reported seeking information from online websites, with notable gender differences in the sources of information. Girls and women were more likely to consult health care professionals , whereas boys and men predominantly used online forums like Reddit and YouTube.

"It is critical for health care, public health, and policymaking professionals to understand where young people are accessing information on muscle-building supplements to inform harm reduction approaches ," says Ganson. "We know that in Canada, regulations of muscle-building supplements are weak and social media companies do not restrict content on muscle-building supplements, which may negatively impact young people's perceptions of the safety and efficacy of muscle-building supplements."

Only 9.8% of participants perceived their use of muscle-building supplements as problematic, with TGE individuals reporting a higher perception of problematic use compared to cisgender participants.

Alarmingly, the study found that nearly two-thirds of participants experienced at least one symptom while using muscle-building supplements, with common symptoms including fatigue, digestive issues, and cardiovascular problems. Despite these symptoms, a staggering 87.8% of those affected did not seek medical attention.

"While we did not specifically assess whether use of muscle-building supplements caused the symptoms experienced by users, it is clear that their physical health symptoms may be relevant for young people to be aware of prior to using muscle-building supplements, and health care professionals should be alerted to these concerning findings," says Ganson.

The findings underscore the need for health care providers to be knowledgeable about muscle-building supplements and to routinely assess their use among adolescents and young adults .

"This is particularly important for TGE and sexual minority individuals, who reported higher symptom rates," says Ganson. "Public health programs should focus on harm reduction education, emphasizing the potential risks of muscle-building supplements and promoting the use of reputable information sources."

Additionally, the study's authors advocate for stronger regulations on the sale and advertisement of muscle-building supplements, particularly on social media platforms.

Explore further

Feedback to editors

Facial thermal imaging and AI can accurately predict presence of coronary artery disease

Study: High excess death rates in the West for 3 years running since start of pandemic despite containment and vaccines

Inflight alcohol plus cabin pressure can lower blood oxygen and raise heart rate, even in the young and healthy

Personalized oxygenation could improve outcomes for patients on ventilators

2 hours ago

Molecule produced in gut can have protective effect against flu, study shows

3 hours ago

Genetic changes identified as key to childhood lupus

New method offers faster, more accurate pathogen identification, even in complex DNA sequences

Oral nucleoside antiviral is progressing toward future pandemic preparedness

4 hours ago

New machine learning method can better predict spine surgery outcomes

Airplane noise exposure may increase risk of chronic disease

Related stories.

Social media giants send mixed signals on muscle-building supplement content

Nov 6, 2023

Commonly used muscle-building dietary supplements are under regulated in Canada, finds study

Sep 12, 2023

Poor sleep health associated with muscle dysmorphia in Canadian young adults

Feb 27, 2024

Conformity to masculine gender norms linked to muscle dysmorphia among young people

Apr 17, 2024

Food insecurity linked to muscle dysmorphia symptoms in adolescent and young adults

Sep 21, 2023

Adverse childhood experiences linked to muscle dysmorphia

Dec 1, 2023

Recommended for you

Pollutants and climate change contribute to millions of deaths from cardiovascular disease each year, warn scientists

6 hours ago

Study indicates fewer than 1 in 4 patients receive dietary counseling after a heart attack

10 hours ago

Let us know if there is a problem with our content

Use this form if you have come across a typo, inaccuracy or would like to send an edit request for the content on this page. For general inquiries, please use our contact form . For general feedback, use the public comments section below (please adhere to guidelines ).

Please select the most appropriate category to facilitate processing of your request

Thank you for taking time to provide your feedback to the editors.

Your feedback is important to us. However, we do not guarantee individual replies due to the high volume of messages.

E-mail the story

Your email address is used only to let the recipient know who sent the email. Neither your address nor the recipient's address will be used for any other purpose. The information you enter will appear in your e-mail message and is not retained by Medical Xpress in any form.

Newsletter sign up

Get weekly and/or daily updates delivered to your inbox. You can unsubscribe at any time and we'll never share your details to third parties.

More information Privacy policy

Donate and enjoy an ad-free experience

We keep our content available to everyone. Consider supporting Science X's mission by getting a premium account.

E-mail newsletter

Study reveals partial reps just as effective for muscle growth

I n fitness, things are always changing with new research updating our knowldge on the effectiveness of different exercise techniques. A recent big review of multiple studies has some interesting information for building muscle. This deep dive into 23 different experiments found out that doing shorter moves (or partial reps) when lifting can pump up one's muscles just as much as doing the longer, full ones.

Full reps vs. partial reps: shaking up the norm in weightlifting

When people hit the gym to lift weights , there is a lot of focus on doing each exercise through its full range of motion. For example, think of a squat . A full rep would mean lowering yourself down until your thighs are parallel to the floor (or even lower) and then coming back up.

On the other hand, a partial rep might only see you going halfway down before coming back up. Up until this point, everyone believed that full reps were the only way to go if you wanted to see gains in muscle size, strength, and sports skills. But this fresh study is shaking things up by showing that partial reps can do the job just as well.

The study examined more than just muscle size. It looked at how these different styles of training affected body fat and sports performance too. What is fascinating is that both full and partial ranges of motion had similar impacts on these areas as well. However, full reps might still have the edge when it comes to improving power, a key component of many athletic movements.

Full or partial reps for different needs

Power, in the fitness world, is the combination of strength and speed - imagine jumping high or throwing fast. The study noted a slight advantage for full reps in this area, probably because using a greater range of motion engages more of the muscles and joints, possibly enhancing how your muscles and brain work together.

Interestingly, the researchers pointed out that partial reps done at longer muscle lengths (think stretching your arm almost fully but not quite) could potentially be even more beneficial for muscle growth than full reps.

This is because stretching a muscle out might lead to more tension (a good kind of tension) that activates growth pathways in your muscles. It is the kind of insight that adds a new layer to how we think about training for size versus strength.

This discovery suggests that the 'best' way to lift weights might vary depending on what each person needs or wants from their workouts. It's particularly good news for individuals who might not be able to do full reps due to injuries or other limitations; they can still make gains with partial repetition.

This study reminds us that our workout plans should be as unique as we are. Everybody's different, and so is the way we react to training. This proves there is no clear-cut, one-way route in fitness. The aim is not to find a flawless formula, but rather to discover what suits you - be it full reps, partial, or a combo of both. Lastly, it is crucial to note that, as with all research, this study comes with its caveats. The trials reviewed were relatively short-term and involved a limited number of participants.

The nuanced nature of the study's outcomes, like the difference in effectiveness for power versus muscle size, suggests that more research is needed to fully understand when and for whom partial reps might be most beneficial.

As fitness keeps changing, this kind of study shifts the conversation, promotes adaptability, and champions different ways of working out. So, if you are a gym pro or a newbie, remember one thing: there's more than one path to getting those muscles built.

• Departments, units, and programs
• College leadership
• Faculty and staff resources
• Inclusive Excellence
• LAS Strategic Plan

• Apply to LAS
• Liberal arts & sciences majors
• LAS Insider blog
• Admissions FAQs
• Parent resources
• Pre-college summer programs

Quick Links

Request info

• Academic policies and standing
• Advising and support
• College distinctions
• Dates and deadlines
• Intercollegiate transfers
• LAS Lineup student newsletter
• Programs of study
• Scholarships
• Certificates
• Student emergencies

Student resources

• Access and Achievement Program
• Career services
• First-Year Experience
• Honors program
• International programs
• Internship opportunities
• Paul M. Lisnek LAS Hub
• Student research opportunities
• Expertise in LAS
• Research facilities and centers
• Dean's Distinguished Lecture series
• Alumni advice
• Alumni award programs
• Get involved
• LAS Alumni Council
• LAS@Work: Alumni careers
• Study Abroad Alumni Networks
• Update your information
• Nominate an alumnus for an LAS award
• Faculty honors
• The Quadrangle Online
• LAS News email newsletter archive
• LAS social media
• Media contact in the College of LAS
• LAS Landmark Day of Giving
• About giving to LAS
• Building projects
• Corporate engagement
• Faculty support
• Lincoln Scholars Initiative
• Impact of giving
• Diversity, equity, and inclusion

Researchers: Nerves prompt muscle to release factors that boost brain health

Exercise prompts muscles to release molecular cargo that boosts brain cell function and connection, but the process is not well understood. New research from the University of Illinois Urbana-Champaign found that the nerves that tell muscles to move also prompt them to release more of the brain-boosting factors.

“The molecules released from the muscle go into the bloodstream and then to the brain, producing so-called crosstalk between the muscle and brain. But the muscle itself is highly innervated. So we wondered, what is the effect of the neurons on this activity of the muscle, and further down to the communication between muscle and brain?” said chemical and biomolecular engineering professor Hyunjoon Kong, leader of the study published in the Proceedings of the National Academy of Sciences. 

“As we get older, we lose these neurons from the muscle. And some people also lose these neurons to disease or injury. So understanding their role, and how these nerves to the muscle affect the brain, is important for older people or patients with neuromuscular injuries and diseases,” he said.

Research on exercise has found that muscles secrete hormones and extracellular vesicles, tiny packages that carry molecules between cells, containing small fragments of RNA that enhance connection, signal transmission and communication between brain cells. However, while much attention has been paid to the function of muscle-derived factors, the role of the nerves that stimulate the muscle is poorly understood, said graduate student Kai-Yu Huang, the first author of the study. 

To fill this gap, the researchers compared two muscle tissue models — one with neuron innervation and one without. They found that the innervated muscle produced more molecules that promote brain neuron activity and regulate muscle development than the muscle without nerves.

Then, the researchers stimulated the nerves with glutamate, a neurotransmitter. They found that the innervated muscle had greater expression of a gene important for regulating secretion. Correspondingly, it emitted higher levels of the hormone irisin, which is associated with beneficial effects of exercise, and released more extracellular vesicles than plain muscle. 

“We analyzed the cargo carried in the vesicles, and we found that there was a greater diversity of microRNA associated with impact on neurodevelopment,” said Huang. “These findings highlight the importance of neuron innervation. As we get older, we lose nerve supply to muscle, and our muscles start to break down and lose function. And somehow, this can further result in organ dysfunction. So understanding how to regulate or maintain muscle’s secreting behavior is very important.”

Next, the researchers plan to look further into mechanisms at the junction where the neurons meet the muscle cells to determine how nerve impulses are stimulating the muscle and whether they affect the production of the brain-boosting factors or just their release, an important distinction for possible treatments for those who have lost nerves or muscle. They also hope to explore using their tissue model as a platform for effectively producing the factors. Ultimately, they hope to have a complete picture of the brain-nerve-muscle loop and how to maintain it.

“It’s our individual organs talking to each other: The brain tells the nerves to stimulate the muscle, and the muscle releases back molecules beneficial for brain function,” Kong said. ”It underscores the importance of exercise. Exercise creates a more robust interface between motor neurons and muscle, and now we know the nerves sending the signal into the muscle releases the molecules and extracellular vesicles that are beneficial to the brain. So we could look at the benefits of exercise focused on fostering that connection more than simply increasing the volume or strength of the muscle.” 

The National Science Foundation, the National Institutes of Health, the Alzheimer’s Disease Association and the Chan Zuckerberg Biohub Chicago supported this work. Illinois faculty who co-authored the study include mechanical science and engineering professor Mattia Gazzola, cell and developmental biology professor Martha Gillette, electrical and computer engineering professor Gabriel Popescu (published posthumously), molecular and integrative physiology processor Hee Jung Chung, bioengineering professor and dean of The Grainger College of Engineering Rashid Bashir, chemistry professor Jonathan Sweedler and materials science and engineering professor Qian Chen. Professor Sung Gap Im at the Korea Advanced Institute of Science and Technology also was a co-author. 

News Source

Read more news

• Privacy Notice
• Accessibility

• News, Analysis & Insights on Nutrition, Supplements, and Health

Supplementation with a blend of botanical extracts found to increase muscle strength and endurance post-resistance training – GNC-funded study

29-May-2024 - Last updated on 29-May-2024 at 02:33 GMT

• Email to a friend

Progressive RET is a well-established workout method that not only improves athletic outcomes, but is also said to support muscle function and overall health of non-athletes.

Sphaeranthus indicus ​ (East Indian globe thistle) flower and Mangifera indica ​ (mango) tree bark are widely used in Ayurvedic medicine due to their immunomodulatory, antioxidant, and anti-inflammatory properties.

A randomised, double-blind, placebo-controlled study funded by General Nutrition Centre Inc (GNC) sought to elucidate the effect of a S. indicus ​ and M. indica ​ extract blend (SMI) on RET outcomes.

SMI is commercially available as GNC’s MyoTOR and PLT Health Solutions’ RipFACTOR.  

A total of 99 men completed the trial after they were randomly assigned to one of four groups: (A1) 425mg of SMI and one RET set, (A2) 850mg of SMI and one RET set, (P1) placebo and one RET set, and (P2) placebo and two RET sets.

The participants were asked to consume two capsules every morning for 56 days.

The RET set included six to eight bench press (BP) and leg extension (LE) repetitions, and was carried out three times a week during the intervention period.

It was found that all groups significantly (p < 0.05) improved BP strength from baseline, but the SMI groups lifted more weight than the placebo groups.

In addition, total muscle strength of both A1 and A2 groups increased compared to P1 (p < 0.001) at all measured time points.

Muscle endurance was measured as repetitions to failure (RTF), which was determined by the maximal number of repetitions a participant completed when lifting 80% of the established baseline — progressive one repetition maximum (1-RM) — until failure.

All groups showed improved muscular endurance, as the number of BP-RTF and LE-RTF increased over time (p < 0.001 for each group).

A2 significantly (p < 0.05) improved BP-RTF compared to P1 on days 28 and 56, and compared to P2 on day 56. For LE-RTF, a treatment effect started showing on day 28 (p = 0.071) but only reached significance (p = 0.005) on day 56.

Furthermore, only A1 and A2 had significantly elevated serum values of total testosterone (TT) and free testosterone (FT) from baseline to day 56. The final FT and TT values for both groups were significantly raised compared to P1, but not P2.

On the other hand, cortisol levels in A2 were found to be lower than P2 (p < 0.05).

“Overall, daily supplementation with either 425 or 850mg of SMI was well-tolerated and accentuated muscle adaptation when used by healthy young men in a progressive eight-week RET programme,” ​the authors wrote.

The inclusion of a second placebo group underscores that the significant differences between the supplementation and placebo groups were not simply the results of different physical efforts.

“In fact, it affirms the notion that the efficacy of SMI was comparable to performing an additional set of exercises in untrained individuals. ​

“This suggests that SMI supplementation may be beneficial for other populations seeking to augment muscle responses to RET — for example, those who habitually participate in RET but whose adaptive responses have stalled.” ​

Potential to benefit wider populations ​

During RET, muscle fibres contract against weighted loads, creating mechanical signals that converge alongside other intracellular signals onto the protein kinase mTOR, which is closely involved in directing the rate of post-exercise muscle protein synthesis.

However, RET-generated mechanical signalling can result in drastically different strength outcomes between individuals, even when their trainings are of similar intensity.

Therefore, people engaged in weight lifting often modify their diet and/or use dietary supplements in an attempt to facilitate anabolic responses to their training efforts.

Safe, conveniently dosed, and plant-based products are also increasingly being explored for their ability to support RET responses.

Mangiferin ​, a bioactive component derived primarily from M. indica ​, may activate nitric oxide (NO) within vascular endothelial cells.

NO is a signalling molecule that can influence mitochondrial function and modulate skeletal muscle activity, and NO precursors could stimulate muscle protein synthesis and muscle growth, particularly when combined with exercise.

Additionally, S. indicus ​ and M. indica ​ are both known for their antioxidant properties and may help scavenge oxidants generated in the actively contracting muscles.

Despite the elevation of TT and FT in the A1 and A2 groups in this study, RET has been shown to bring no or limited transient increase in testosterone levels in women.

As the study only included male participants, the researchers said that future studies should examine how SMI might affect muscular adaptive responses to RET in healthy women, and specifically in women experiencing peri- and postmenopause.

The effect of testosterone is also influenced by circulating cortisol, which plays a fundamental role in skeletal muscle adaptive responses by promoting lipolysis and proteolysis.

A higher testosterone/cortisol (T/C) ratio represents an improved balance between the anabolic and catabolic status of the body, whereas a decreasing T/C ratio often marks exercise-induced stress, physiological strain, and inadequate post-exercise recovery.

Although cortisol levels fell in the supplemented groups, the overall increased T/C ratio in these participants suggests that SMI may improve adaptation to RET regimens.

“Muscle strength and functionality improve a wide array of health outcomes, so further research should be conducted to investigate if similar outcomes are seen in older adults, where muscular atrophy and sarcopenia are increasingly reported to lead to reduced functional capacity, increased frailty, and progressive disability.” ​

Source: Frontiers in Nutrition

https://doi.org/10.3389/fnut.2024.1393917 ​

“A botanical extract blend of Mangifera indica and Sphaeranthus indicus combined with resistance exercise training improves muscle strength and endurance over exercise alone in young men: a randomized, blinded, placebo-controlled trial” ​

Authors: Dawna Salter, et al

Active Lifestyle Nutrition and Healthy Ageing will be key topics of focus at Growth Asia Summit 2024 – join us in Singapore to learn about market opportunities and glean insights from major industry experts. Find out more  ​ here ​ ​ .  ​

Related news

Related products

Women's Health For All Life Stages

Content provided by Gencor | 29-May-2024 | White Paper

SPINS' recent industry trends analysis shows that women's health is finally getting its due after years of being overlooked in favor of men's...

Pycnogenol® for Sport: eNOS and Beyond

Content provided by Horphag Research | 01-May-2024 | White Paper

Engaging in physical activities immediately triggers a number of physiological responses from our body (1). First, our liver glucose output and adipose...

TWK10®: Optimize Muscle Wellness Across Life Stages

Content provided by SYNBIO TECH INC. | 18-Mar-2024 | White Paper

Muscle mass declines 3-8% per decade after 30, accelerating past 60 - impacting mobility, strength, and overall quality of life.

Revolutionizing Brain Health with BioKesum®

Content provided by Biotropics Malaysia | 20-Feb-2024 | Data Sheet

Revitalize the nootropic industry with new clinically proven herbal extract from Kesum leaves shown to improve executive memory, mood and brain markers...

• Human Milk Oligosaccharides (HMOs): A prebiotic fostering a resilient family foundation from cradle to adulthood KYOWA HAKKO BIO SINGAPORE PTE LTD | Download Technical / White Paper
• ABKEFIR™: New Edge in Probiotics & Postbiotics SYNBIO TECH INC. | Download Product Brochure
• Harness the power of algae for omega-3 innovation dsm-firmenich | Download Insight Guide
• Pycnogenol® for Sport: eNOS and Beyond Horphag Research | Download Technical / White Paper
• Unlocking skin health at a cellular level: The science behind glutathione KYOWA HAKKO BIO SINGAPORE PTE LTD | Download Product Brochure
• TWK10®: Optimize Muscle Wellness Across Life Stages SYNBIO TECH INC. | Download Technical / White Paper

On-demand webinars

• Healthy Ageing APAC Webinar
• Mitigating safety: Challenges in pet food manufacturing Webinar
• Premium categories: Does the humanization trend still have legs? Webinar
• Sustainable sourcing: Limiting pet industry impact on ecosystems Webinar
• Mining the microbiome: Balance is everything Webinar

Nutra Champions Podcast

Promotional Features

NutraIngredients-Asia

• Advertise with us
• Apply to reuse our content
• Press Releases – Guidelines
• Contact the Editor
• Report a technical problem
• Subscription Benefits
• Why Register
• Whitelist our newsletters
• Editorial Calendar
• Event Calendar
• Expert advisory panel

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

• View all journals
• Explore content
• About the journal
• Publish with us
• Sign up for alerts
• Published: 28 May 2024

Time of exercise differentially impacts bone growth in mice

• Shaoling Yu 1 , 2 , 3   na1 ,
• Qingming Tang 1 , 2 , 3   na1 ,
• Xiaofeng Lu 1 , 2 , 3 ,
• Guangjin Chen 1 , 2 , 3 ,
• Mengru Xie 1 , 2 , 3 ,
• Jingxi Yang 1 , 2 , 3 ,
• Ying Yin 1 , 2 , 3 ,
• Wenhao Zheng 1 , 2 , 3 ,
• Jinyu Wang   ORCID: orcid.org/0000-0002-5081-8850 1 , 2 , 3 ,
• Yunyun Han   ORCID: orcid.org/0000-0003-2336-167X 4 ,
• Luoying Zhang   ORCID: orcid.org/0000-0001-5996-6975 5 &
• Lili Chen   ORCID: orcid.org/0000-0002-9965-8990 1 , 2 , 3  

Nature Metabolism ( 2024 ) Cite this article

662 Accesses

17 Altmetric

Metrics details

• Bone development
• Circadian rhythms
• Homeostasis

Although physical training has been shown to improve bone mass, the time of day to exercise for optimal bone growth remains uncertain. Here we show that engaging in physical activity during the early active phase, as opposed to the subsequent active or rest phase, results in a more substantial increase in bone length of male and female mice. Transcriptomic and metabolomic methodologies identify that exercise during the early active phase significantly upregulates genes associated with bone development and metabolism. Notably, oxidative phosphorylation-related genes show a rhythmic expression in the chondrification centre, with a peak at the early active phase, when more rhythmic genes in bone metabolism are expressed and bone growth is synergistically promoted by affecting oxidative phosphorylation, which is confirmed by subsequent pharmacological investigations. Finally, we construct a signalling network to predict the impact of exercise on bone growth. Collectively, our research sheds light on the intricacies of human exercise physiology, offering valuable implications for interventions.

This is a preview of subscription content, access via your institution

Access options

Access Nature and 54 other Nature Portfolio journals

Get Nature+, our best-value online-access subscription

24,99 € / 30 days

cancel any time

Subscribe to this journal

Receive 12 digital issues and online access to articles

111,21 € per year

only 9,27 € per issue

Buy this article

• Purchase on Springer Link
• Instant access to full article PDF

Prices may be subject to local taxes which are calculated during checkout

Similar content being viewed by others

Investigating nutrient biomarkers of healthy brain aging: a multimodal brain imaging study

Temporal dynamics of the multi-omic response to endurance exercise training

Adipose tissue as a linchpin of organismal ageing

Data availability.

Transcriptome raw data of this study have been deposited in the Genome Sequence Archive 53 in the National Genomics Data Center 54 , China National Center for Bioinformation/Beijing Institute of Genomics, Chinese Academy of Sciences, and will be publicly available under accession code CRA015794 on 08 April 2026. Source data are provided with this paper.

Jacobi, L. & Cash, T. F. In pursuit of the perfect appearance: discrepancies among self-ideal percepts of multiple physical attributes. J. Appl. Social Psychol. 24 , 379–396 (1994).

McCormack, S. E. et al. Association between linear growth and bone accrual in a diverse cohort of children and adolescents. JAMA Pediatr. 171 , e171769 (2017).

Article   PubMed   PubMed Central   Google Scholar  

Alves, J. G. B. & Alves, G. V. Effects of physical activity on children’s growth. J. Pediatr. 95 , 72–78 (2019).

Article   Google Scholar  

Karlsson, M. K. & Rosengren, B. E. Exercise and peak bone mass. Curr. Osteoporos. Rep. 18 , 285–290 (2020).

Bouillon, R. et al. Skeletal and extraskeletal actions of vitamin D: current evidence and outstanding questions. Endocr. Rev. 40 , 1109–1151 (2019).

Article   PubMed   Google Scholar  

Tong, X. et al. The effect of exercise on the prevention of osteoporosis and bone angiogenesis. BioMed. Res. Int. 2019 , 8171897 (2019).

Gabriel, B. M. & Zierath, J. R. Circadian rhythms and exercise - re-setting the clock in metabolic disease. Nat. Rev. Endocrinol. 15 , 197–206 (2019).

Arciero, P. J. et al. Morning exercise reduces abdominal fat and blood pressure in women; evening exercise increases muscular performance in women and lowers blood pressure in men. Front. Physiol. 13 , 893783 (2022).

Casanova-Vallve, N. et al. Daily running enhances molecular and physiological circadian rhythms in skeletal muscle. Mol. Metab. 61 , 101504 (2022).

Article   CAS   PubMed   PubMed Central   Google Scholar  

Savikj, M. et al. Afternoon exercise is more efficacious than morning exercise at improving blood glucose levels in individuals with type 2 diabetes: a randomised crossover trial. Diabetologia 62 , 233–237 (2019).

Article   CAS   PubMed   Google Scholar  

Schumacher, L. M., Thomas, J. G., Raynor, H. A., Rhodes, R. E. & Bond, D. S. Consistent morning exercise may be beneficial for individuals with obesity. Exerc. Sport Sci. Rev. 48 , 201–208 (2020).

Kronenberg, H. M. Developmental regulation of the growth plate. Nature 423 , 332–336 (2003).

Hollander, J. M. & Zeng, L. The emerging role of glucose metabolism in cartilage development. Curr. Osteoporos. Rep. 17 , 59–69 (2019).

Stegen, S. et al. HIF-1α metabolically controls collagen synthesis and modification in chondrocytes. Nature 565 , 511–515 (2019).

Zheng, L., Zhang, Z., Sheng, P. & Mobasheri, A. The role of metabolism in chondrocyte dysfunction and the progression of osteoarthritis. Ageing Res. Rev. 66 , 101249 (2021).

Sato, S. et al. Time of exercise specifies the impact on muscle metabolic pathways and systemic energy homeostasis. Cell Metab. 30 , 92–110 (2019).

Fan, W. & Evans, R. M. Exercise mimetics: impact on health and performance. Cell Metab. 25 , 242–247 (2017).

Cantó, C. et al. AMPK regulates energy expenditure by modulating NAD + metabolism and SIRT1 activity. Nature 458 , 1056–1060 (2009).

Yu, S. et al. Circadian rhythm modulates endochondral bone formation via MTR1/AMPKβ1/BMAL1 signaling axis. Cell Death Differ. 29 , 874–887 (2022).

van der Lee, R. et al. Transcriptome analysis of complex I-deficient patients reveals distinct expression programs for subunits and assembly factors of the oxidative phosphorylation system. BMC Genomics 16 , 691 (2015).

Troy, K. L., Mancuso, M. E., Butler, T. A. & Johnson, J. E. Exercise early and often: effects of physical activity and exercise on women’s bone health. Int. J. Environ. Res. Public Health 15 , 878 (2018).

Bass, J. & Takahashi, J. S. Circadian integration of metabolism and energetics. Science 330 , 1349–1354 (2010).

Tan, V. P. et al. Influence of physical activity on bone strength in children and adolescents: a systematic review and narrative synthesis. J. Bone Miner. Res. 29 , 2161–2181 (2014).

Yu, S. et al. Circadian BMAL1 regulates mandibular condyle development by hedgehog pathway. Cell Prolif. 53 , e12727 (2020).

Sato, S. et al. Atlas of exercise metabolism reveals time-dependent signatures of metabolic homeostasis. Cell Metab. 34 , 329–345 (2022).

Schroeder, A. M. et al. Voluntary scheduled exercise alters diurnal rhythms of behaviour, physiology and gene expression in wild-type and vasoactive intestinal peptide-deficient mice. J. Physiol. 590 , 6213–6226 (2012).

Qi, Z., Liu, W. & Lu, J. The mechanisms underlying the beneficial effects of exercise on bone remodeling: roles of bone-derived cytokines and microRNAs. Prog. Biophys. Mol. Biol. 122 , 131–139 (2016).

Herrmann, M. et al. Interactions between muscle and bone-where physics meets biology. Biomolecules 10 , 432 (2020).

Kirk, B., Feehan, J., Lombardi, G. & Duque, G. Muscle, bone, and fat crosstalk: the biological role of myokines, osteokines, and adipokines. Curr. Osteoporos. Rep. 18 , 388–400 (2020).

Deymier, A. C., Deymier, P. A., Latypov, M. & Muralidharan, K. Effect of stress on the dissolution/crystallization of apatite in aqueous solution: a thermochemical equilibrium study. Philos. Trans. A Math. Phys. Eng. Sci. 381 , 20220242 (2023).

CAS   PubMed   Google Scholar  

Li, X. et al. Stimulation of Piezo1 by mechanical signals promotes bone anabolism. eLife 8 , e49631 (2019).

Pomerants, T., Tillmann, V., Karelson, K., Jürimäe, J. & Jürimäe, T. Impact of acute exercise on bone turnover and growth hormone/insulin-like growth factor axis in boys. J. Sports Med. Phys. Fit. 48 , 266–271 (2008).

CAS   Google Scholar  

Hughes, J. M., Guerriere, K. I., Popp, K. L., Castellani, C. M. & Pasiakos, S. M. Exercise for optimizing bone health after hormone-induced increases in bone stiffness. Front. Endocrinol. 14 , 1219454 (2023).

Scott, A., Khan, K. M., Duronio, V. & Hart, D. A. Mechanotransduction in human bone: in vitro cellular physiology that underpins bone changes with exercise. Sports Med. 38 , 139–160 (2008).

Lee, S. Y., Abel, E. D. & Long, F. Glucose metabolism induced by Bmp signaling is essential for murine skeletal development. Nat. Commun. 9 , 4831 (2018).

Hollander, J. M. et al. A critical bioenergetic switch is regulated by IGF2 during murine cartilage development. Commun. Biol. 5 , 1230 (2022).

Rajpurohit, R., Mansfield, K., Ohyama, K., Ewert, D. & Shapiro, I. M. Chondrocyte death is linked to development of a mitochondrial membrane permeability transition in the growth plate. J. Cell. Physiol. 179 , 287–296 (1999).

Tourmente, M., Varea-Sánchez, M. & Roldan, E. R. S. Faster and more efficient swimming: energy consumption of murine spermatozoa under sperm competition. Biol. Reprod. 100 , 420–428 (2019).

Jin, L. et al. FGF21-Sirtuin 3 axis confers the protective effects of exercise against diabetic cardiomyopathy by governing mitochondrial integrity. Circulation 146 , 1537–1557 (2022).

Wang, B. et al. The mitochondrial Ahi1/GR participates the regulation on mtDNA copy numbers and brain ATP levels and modulates depressive behaviors in mice. Cell Commun. Signal. 21 , 21 (2023).

Li, J., King, N. C. & Sinoway, L. I. Interstitial ATP and norepinephrine concentrations in active muscle. Circulation 111 , 2748–2751 (2005).

Hargreaves, M. & Spriet, L. L. Skeletal muscle energy metabolism during exercise. Nat. Metab. 2 , 817–828 (2020).

Li, E. et al. BMAL1 regulates mitochondrial fission and mitophagy through mitochondrial protein BNIP3 and is critical in the development of dilated cardiomyopathy. Protein Cell 11 , 661–679 (2020).

Wan, M. C. et al. Upregulation of mitochondrial dynamics is responsible for osteogenic differentiation of mesenchymal stem cells cultured on self-mineralized collagen membranes. Acta Biomater. 136 , 137–146 (2021).

Wang, J. et al. Disrupting circadian rhythm via the PER1-HK2 axis reverses trastuzumab resistance in gastric cancer. Cancer Res. 82 , 1503–1517 (2022).

Anderson, G. & Reiter, R. J. Melatonin: roles in influenza, COVID-19, and other viral infections. Rev. Med. Virol. 30 , e2109 (2020).

Zilber, S. et al. Mouse femoral intramedullary injection model: technique and microCT scan validation. J. Biomed. Mater. Res. B Appl. Biomater. 84 , 286–290 (2008).

Wang, Z. X. et al. Aged bone matrix-derived extracellular vesicles as a messenger for calcification paradox. Nat. Commun. 13 , 1453 (2022).

Welz, P. S. et al. BMAL1-driven tissue clocks respond independently to light to maintain homeostasis. Cell 177 , 1436–1447 (2019).

Kumar, L. & E Futschik, M. Mfuzz: a software package for soft clustering of microarray data. Bioinformation 2 , 5–7 (2007).

Stegen, S., Moermans, K., Stockmans, I., Thienpont, B. & Carmeliet, G. The serine synthesis pathway drives osteoclast differentiation through epigenetic regulation of NFATc1 expression. Nat. Metab. 6 , 141–152 (2024).

Chen, G. et al. Developmental growth plate cartilage formation suppressed by artificial light at night via inhibiting BMAL1-driven collagen hydroxylation. Cell Death Differ. 30 , 1503–1516 (2023).

Chen, T. et al. The genome sequence archive family: Toward explosive data growth and diverse data types. Genomics Proteomics Bioinformatics 19 , 578–583 (2021).

CNCB-NGDC Members and Partners. Database resources of the National Genomics Data Center, China National Center for Bioinformation in 2024. Nucleic Acids Res . 52 , D18–D32 (2024).

Download references

Acknowledgements

This research was supported by the National Natural Science Foundation of China (U23A20443, 31725011 and 82030070 to L.C. and 82100960 to S.Y.) and the National Key Research and Development Program of China (2021YFC2400404 to L.C.).

Author information

These authors contributed equally: Shaoling Yu, Qingming Tang.

Authors and Affiliations

Department of Stomatology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China

Shaoling Yu, Qingming Tang, Xiaofeng Lu, Guangjin Chen, Mengru Xie, Jingxi Yang, Ying Yin, Wenhao Zheng, Jinyu Wang & Lili Chen

School of Stomatology, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China

Hubei Province Key Laboratory of Oral and Maxillofacial Development and Regeneration, Wuhan, China

Department of Neurobiology, School of Basic Medicine and Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China

Key Laboratory of Molecular Biophysics of Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China

Luoying Zhang

You can also search for this author in PubMed   Google Scholar

Contributions

Concept and design, S.Y. and L.C.; experimentation, S.Y., X.L., G.C., J.Y. and W.Z.; acquisition, analysis or interpretation of data, S.Y., Q.T., X.L., G.C., M.X., J.Y., Y.Y., W.Z., J.W. and L.Z.; drafting of the manuscript, S.Y. and Q.T.; critical revision of the manuscript for important intellectual content, L.C., L.Z. and Y.H.; supervision, L.C.; funding acquisition, L.C. and S.Y. All authors reviewed the manuscript.

Corresponding author

Correspondence to Lili Chen .

Ethics declarations

Competing interests.

The authors declare no competing interests.

Peer review

Peer review information.

Nature Metabolism thanks the anonymous reviewers for their contribution to the peer review of this work. Primary Handling Editor: Ashley Castellanos-Jankiewicz, in collaboration with the Nature Metabolism team.

Additional information

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Extended data

Extended data fig. 1 exercise during the early active phase can robustly expedite bone growth..

a, b , Food intake (a) and body weight (b) of sedentary (Sed) and exercise (Exe) mice (n = 12, Sed, Exe at ZT1, ZT5, and ZT 13 mice; n = 8, Exe at ZT9 mice; n = 11, Exe at ZT17 mice; n = 10, Exe at ZT21 mice; Data were presented as mean ± SD and analyzed using one-way ANOVA with Tukey multiple comparisons test). c , Images of calcein double labeling of the femoral diaphyseal cortical bones of Sed and Exe mice. Scale bar, 100 μm. d, e , Quantification of mineralization apposition rate (MAR) and bone formation rate (BFR) of the femoral metaphyseal cortical bones (n = 3 biologically independent experiments, Data were presented as mean ± SD and analyzed using one-way ANOVA with Tukey multiple comparisons test).

Source data

Extended data fig. 2 exercise during the early active phase can robustly expedite bone growth in female mice..

a , Scheme of exercise applied in this study. The female mice were subjected to treadmill running following a 5-day per week acclimatization protocol at ZT1, ZT5, ZT9, ZT13, ZT17, and ZT21, respectively. b , Three-dimensional visualization of femora from micro-CT images of sedentary and exercise mice at ZT1, ZT5, ZT9, ZT13, ZT17, and ZT21. The red boxes indicate the levels of cartilaginous osteogenesis tissues. c , Micro-CT analysis of the total length, bone volume / total volume (BV/TV), and trabecular thickness (Tb.Th) of femora (n = 5). d , Representative images of S-O staining of the distal femora in sedentary and exercise mice. Scale bar, 50 μm. e – h , The height of proliferation zone (PZ), hypertrophic zone (HZ), and chondrocyte number per column in the PZ and HZ of growth plate cartilages (n = 3 biologically independent experiments). i , j , EdU staining analysis of proliferating cells in PZ from the growth plate cartilages. Arrowheads indicate EdU+ cells (n = 3). Scale bar, 50 μm. It is the growth plate cartilages between the white lines. k , Images of calcein double labeling of the femoral metaphyseal cancellous bones of sedentary and exercise mice. Scale bar, 100 μm. l , Quantification of mineralization apposition rate (MAR) of the femoral metaphyseal cancellous bones (n = 3 biologically independent experiments). The white line is the calcein deposit of the first injection, and the red line is the second injection. c, e-h, j, l, Data were presented as mean ± SD and analyzed using one-way ANOVA with the Tukey multiple comparisons test.

Extended Data Fig. 3 Exercise at ZT13 in Synergy with Intrinsic Bone Metabolic Rhythms Activates the Expression of Bone Growth-Related Genes.

a , Heatmaps displaying rhythmic transcripts before and after exercise during the rest phase (ZT1, ZT5) or active phase (ZT13, ZT17, ZT21). b , GO analysis of rhythmic transcripts both in Sed and Exe. Numbers within the charts indicate number of transcripts identified within each biological pathway. c , Heatmaps displaying rhythmic transcripts before and after exercise in bone development (left), metabolic process (middle) and glucose metabolic process (right) after exercise during the early active phase (ZT13).

Extended Data Fig. 4 Exercise at ZT13 Enhances the Association between OXPHOS and Bone Growth.

a , KEGG analysis of the top 30 pathways after exercise at the early active phase. b , The network of the DEGs among top enriched pathway. c , d , Radar plots representing the DEGs related to glycolysis and oxidative phosphorylation after exercise at the early rest phase (c) and early active phase (d). e , f , Sankey diagram for glycolysis (e) and oxidative phosphorylation (f)- ossification interaction after exercise at the active phase (ZT13, ZT17, ZT21) and early rest phase (ZT1).

Extended Data Fig. 5 Oxidative Phosphorylation Is Markedly Activated by Exercise during the Early Active Phase.

a , b , Heatmap of representational DEGs related to oxidative phosphorylation (a) and glycolysis (b). c , d , qRT-PCR analysis of the mRNA levels of Atp6v0c1, Cox11, Ndufv3, Ldha, Pfkp, and Adh7 at indicated time. Differential rhythmicity analysis performed with the 1-component cosinor analysis. The false discovery rate (FDR) method was applied for adjustment, adjusted P values correspond to the statistical significance of amplitude changes in Exe versus Sed mice at the early rest and active phase (n = 4 biologically independent experiments, Data were presented as mean ± SD). e , f , Western blot analysis of the levels of ATP6V0D1 and PFKP in the femoral metaphysis tissue from Sed and Exe mice during the early rest versus active phase (n = 3 biologically independent experiments, Data were presented as mean ± SD and analyzed using two-way ANOVA with Tukey multiple comparisons test). g , Immunofluorescence of PFKP in the growth plate cartilages after exercise during the early rest versus active phase. Scale bar, 50 μm. One technical replicate of three biological replicates for each group.

Extended Data Fig. 6 Physical Activity during the Active Phase Stimulates Bone Growth through the Process of Oxidative Phosphorylation.

a , The schematic shows mice injected with oxidative phosphorylation inhibitor (oligomycinA, Selleckchem, 15 mg/kg/d, intraperitoneal injection) or equal solvent 60 minutes before exercise. b , Representative images of micro-CT reconstruction of femora from Sed and Exe mice with or without oxidative phosphorylation inhibitor injection. c , Micro-CT analysis of the total femora length, BV/TV, Tb.Th, and Tb.N of Sed and Exe mice injected oxidative phosphorylation inhibitor or equal solvent (n = 5 biologically independent experiments). d , e , Representative images of S-O staining of the distal femora in Sed and Exe mice injected with oxidative phosphorylation inhibitor or equal solvent (n = 3 biologically independent experiments). Scale bar, 50 μm. f , g , EdU staining of proliferating cells in PZ from the growth plate cartilages in Sed and Exe mice injected oxidative phosphorylation inhibitor or equal solvent. Arrowheads indicate EdU+ cells (n = 3 biologically independent experiments). Scale bar, 50 μm. c, e, g, Data were presented as mean ± SD and analyzed using two-way ANOVA with the Tukey multiple comparisons test.

Extended Data Fig. 7 Physical Activity during the Active Phase Stimulates Bone Growth through the Process of Oxidative Phosphorylation.

a , Adenosine triphosphate (ATP) production of femur in Sed and Exe mice intraperitoneally injected oxidative phosphorylation inhibitor or equal solvent (n = 3 biologically independent experiments). b , The content of NAD+ and NADH, and the ratio of NAD + / NADH of femur in Sed and Exe mice injected oxidative phosphorylation inhibitor or equal solvent (n = 3 biologically independent experiments). c , d , Western blot analysis of the levels of ATP6V0D1, Cyclin D2, SOX9 and COL2α1 in the femoral metaphysis tissue from Sed and Exe mice injected oxidative phosphorylation inhibitor (oligomycin A) or equal solvent during the early rest versus active phase (n = 3 biologically independent experiments). e , f , Immunofluorescence of COL2α1 and ACAN in the growth plate cartilages after exercise during the early rest versus active phase with or without oxidative phosphorylation inhibitor injection. Scale bars, 50 μm. One technical replicate of three biological replicates for each group. a, b, d, Data were presented as mean ± SD and analyzed using two-way ANOVA with Tukey multiple comparisons test.

Extended Data Fig. 8 Stimulating Oxidative Phosphorylation Pharmacologically during the Early Active Phase Enhances Bone Growth.

a , ATP production of femur in Sed and Exe mice intraperitoneally injected oxidative phosphorylation activator or equal solvent (n = 3 biologically independent experiments). b , The content of NAD+ and NADH, and the ratio of NAD + / NADH of femur in Sed and Exe mice intraperitoneally injected oxidative phosphorylation activator or equal solvent (n = 3 biologically independent experiments). c , d , Western blot analysis of the levels of AMPKα1/α2, p-AMPKα1/α2, ATP6V0D1, COX IV, Cyclin D2, COL2α1 and ACAN in the femoral metaphysis tissue from Sed and Exe mice intraperitoneally injected oxidative phosphorylation activator or equal solvent (n = 6 biologically independent experiments). a, b, d, Data were presented as mean ± SD and analyzed using two-way ANOVA with Tukey multiple comparisons test.

Extended Data Fig. 9 Stimulating Oxidative Phosphorylation Pharmacologically during the Early Active Phase Enhances Bone Growth.

a , ATP production of femur in Sed and Exe mice intramedullary injected oxidative phosphorylation activator or equal solvent (n = 3 biologically independent experiments). b , The content of NAD+ and NADH, and the ratio of NAD + / NADH of femur in Sed and Exe mice intramedullary injected oxidative phosphorylation activator or equal solvent (n = 3 biologically independent experiments). c , d , Western blot analysis of the levels of AMPKα1/α2, p-AMPKα1/α2, ATP6V0D1, COX IV, Cyclin D2, COL2α1 and ACAN in the femoral metaphysis tissue from Sed and Exe mice intramedullary injected oxidative phosphorylation activator or equal solvent (n = 3 biologically independent experiments). a, b, d, Data were presented as mean ± SD and analyzed using two-way ANOVA with Tukey multiple comparisons test.

Extended Data Fig. 10 Stimulating Oxidative Phosphorylation Pharmacologically during the Early Active Phase Enhances Bone Growth.

a , Representative images of micro-CT reconstruction of femora from Sed and Exe mice with or without oxidative phosphorylation activator injection (AICAR, Selleckchem, 50 mg/kg/d, a total of 28 days, intramedullary injection). b , Micro-CT analysis of the total femora length, BV/TV, Tb.Th, and Tb.N of Sed and Exe mice intramedullary injected oxidative phosphorylation activator or equal solvent (n = 5 biologically independent experiments). c , d , Representative images of S-O staining of the distal femora in Sed and Exe mice intramedullary injected with oxidative phosphorylation activator or equal solvent (n = 3 biologically independent experiments). Scale bar, 50 μm. e , f , EdU staining of proliferating cells in PZ from the growth plate cartilages in Sed and Exe mice intramedullary injected oxidative phosphorylation activator or equal solvent. Arrowheads indicate EdU+ cells (n = 3 biologically independent experiments). Scale bar, 50 μm. g , h , Immunofluorescence of COL2α1 and ACAN in the growth plate cartilages after exercise at the early rest versus active phase with or without oxidative phosphorylation activator intramedullary injection. Scale bars, 50 μm. b, d, f, Data were presented as mean ± SD and analyzed using two-way ANOVA with the Tukey multiple comparisons test.

Supplementary information

Supplementary information.

Supplementary Figs. 1–3 and Supplementary Tables 1–3.

Reporting Summary

Supplementary data 1.

Statistical source data Supplementary Fig. 2.

Supplementary Data 2

Unprocessed western blots Supplementary Fig. 2.

Supplementary Data 3

Statistical source data Supplementary Fig. 3.

Source Data Fig. 1

Statistical source data.

Source Data Fig. 2

Unprocessed western blots.

Source Data Fig. 3

Source data fig. 4, source data fig. 5, source data fig. 6, source data extended data fig. 1, source data extended data fig. 2, source data extended data fig. 4, source data extended data fig. 5, source data extended data fig. 6, source data extended data fig. 7, source data extended data fig. 8, source data extended data fig. 9, source data extended data fig. 10, rights and permissions.

Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.

Reprints and permissions

About this article

Cite this article.

Yu, S., Tang, Q., Lu, X. et al. Time of exercise differentially impacts bone growth in mice. Nat Metab (2024). https://doi.org/10.1038/s42255-024-01057-0

Download citation

Received : 22 April 2023

Accepted : 26 April 2024

Published : 28 May 2024

DOI : https://doi.org/10.1038/s42255-024-01057-0

Share this article

Anyone you share the following link with will be able to read this content:

Sorry, a shareable link is not currently available for this article.

Provided by the Springer Nature SharedIt content-sharing initiative

Quick links

• Explore articles by subject
• Guide to authors
• Editorial policies

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

2024 Environmental Performance Index: A Surprise Top Ranking, Global Biodiversity Commitment Tested

The Baltic nation of Estonia is No. 1 in the 2024 rankings, while Denmark, one of the top ranked countries in the 2022 EPI dropped to 10 th place, highlighting the challenges of reducing emissions in hard-to-decarbonize industries. Meanwhile, “paper parks” are proving a global challenge to international biodiversity commitments.

  Listen to Article

In 2022, at the UN Biodiversity Conference, COP 15, in Montreal over 190 countries made what has been called “the biggest conservation commitment the world has ever seen.”  The Kunming-Montreal Global Biodiversity Framework called for the effective protection and management of 30% of the world’s terrestrial, inland water, and coastal and marine areas by the year 2030 — commonly known as the 30x30 target. While there has been progress toward reaching this ambitious goal of protecting 30% of land and seas on paper, just ahead of World Environment Day, the 2024 Environmental Performance Index (EPI) , an analysis by Yale researchers that provides a data-driven summary of the state of sustainability around the world, shows that in many cases such protections have failed to halt ecosystem loss or curtail environmentally destructive practices.

A new metric that assesses how well countries are protecting important ecosystems indicated that while nations have made progress in protecting land and seas, many of these areas are “paper parks” where commercial activities such as mining and trawling continue to occur — sometimes at a higher rate than in non-protected areas. The EPI analyses show that in 23 countries, more than 10% of the land protected is covered by croplands and buildings, and in 35 countries there is more fishing activity inside marine protected areas than outside. 

“Protected areas are failing to achieve their goals in different ways,” said Sebastián Block Munguía, a postdoctoral associate with the Yale Center for Environmental Law and Policy (YCELP) and the lead author of the report. “In Europe, destructive fishing is allowed inside marine protected areas, and a large fraction of the area protected in land is covered by croplands, not natural ecosystems. In many developing countries, even when destructive activities are not allowed in protected areas, shortages of funding and personnel make it difficult to enforce rules.”

The 2024 EPI, published by the Yale Center for Environmental Law and Policy and Columbia University’s Center for International Earth Science Information Network ranks 180 countries based on 58 performance indicators to track progress on mitigating climate change, promoting environmental health, and safeguarding ecosystem vitality. The data evaluates efforts by the nations to reach U.N. sustainability goals, the 2015 Paris Climate Change Agreement, as well as the Kunming-Montreal Global Biodiversity Framework. The data for the index underlying different indicators come from a variety of academic institutions and international organizations and cover different periods. Protected area coverage indicators are based on data from March 2024, while greenhouse emissions data are from 2022.

Estonia has decreased its GHG emissions by 59% compared to 1990. The energy sector will be the biggest contributor in reducing emissions in the coming years as we have an aim to produce 100% of our electricity consumption from renewables by 2030.”

The index found that many countries that were leading in sustainability goals have fallen behind or stalled, illustrating the challenges of reducing emissions in hard-to-decarbonize industries and resistant sectors such as agriculture. In several countries, recent drops in agricultural greenhouse gas emissions (GHG) have been the result of external circumstances, not policy. For example, in Albania, supply chain disruptions led to more expensive animal feed that resulted in a sharp reduction in cows and, consequentially, nitrous oxide and methane emissions.

Estonia leads this year’s rankings with a 40% drop in GHG emissions over the last decade, largely attributed to replacing dirty oil shale power plants with cleaner energy sources. The country is drafting a proposal to achieve by 2040 a CO2 neutral energy sector and a CO2 neutral public transport network in bigger cities.

“Estonia has decreased its GHG emissions by 59% compared to 1990. The energy sector will be the biggest contributor in reducing emissions in the coming years as we have an aim to produce 100% of our electricity consumption from renewables by 2030,” said Kristi Klaas, Estonia’s vice-minister for Green Transition. Klaas discussed some of the policies that led to the country's success as well as ongoing challenges, such as reducing emissions in the agriculture sector, at a webinar hosted by YCELP on June 3.  Dr. Abdullah Ali Abdullah Al-Amri, chairman of the Environment Authority of Oman, also joined the webinar to discuss efforts aimed at protecting the county's multiple ecosystems with rare biodiversity and endangered species, such as the Arabian oryx, and subspecies, such as the Arabian leopard. 

Subscribe to “YSE 3”

Biweekly, we highlight three news and research stories about the work we’re doing at Yale School of the Environment.

 Denmark, the top ranked country in the 2022 EPI dropped to 10th place, as its pace of decarbonization slowed, highlighting that those early gains from implementing “low-hanging-fruit policies, such as switching to electricity generation from coal to natural gas and expanding renewable power generation are themselves insufficient,” the index notes. Emissions in the world’s largest economies such as the U.S. (which is ranked 34th) are falling too slowly or still rising — such as in China, Russia, and India, which is ranked 176th.

Over the last decade only five countries — Estonia, Finland, Greece, Timor-Leste, and the United Kingdom — have cut their GHG emissions over the last decade at the rate needed to reach net zero by 2050. Vietnam and other developing countries in Southeast and Southern Asia — such as Pakistan, Laos, Myanmar, and Bangladesh — are ranked the lowest, indicating the urgency of international cooperation to help provide a path for struggling nations to achieve sustainability.

“The 2024 Environmental Performance Index highlights a range of critical sustainability challenges from climate change to biodiversity loss and beyond — and reveals trends suggesting that countries across the world need to redouble their efforts to protect critical ecosystems and the vitality of our planet,” said Daniel Esty, Hillhouse Professor of Environmental Law and Policy and director of YCELP.

• Daniel C. Esty
• Sebastián Block Munguía
• Ecosystem Management and Conservation
• Environmental Policy Analysis

Media Contact

Fran Silverman

Associate Director of Communications

Research in the News

Climate Change Threatens Resilience of Sri Lankan Rainforests

An Inside Look at Beech Leaf Disease

Achieving Sustainable Urban Growth on a Global Scale

Connect with us.

• Request Information
• Register for Events

An official website of the United States government

The .gov means it’s official. Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

The site is secure. The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

• Publications
• Account settings

Preview improvements coming to the PMC website in October 2024. Learn More or Try it out now .

• Advanced Search
• Journal List
• Front Sports Act Living

Resistance Training Variables for Optimization of Muscle Hypertrophy: An Umbrella Review

Roberto bernárdez-vázquez.

1 Faculty of Health Sciences, Universidad Isabel I, Burgos, Spain

Javier Raya-González

Daniel castillo.

2 Valoración del Rendimiento Deportivo, Actividad Física y Salud, y Lesiones Deportivas (REDAFLED), Universidad de Valladolid, Soria, Spain

Marco Beato

3 School of Health and Sports Science, University of Suffolk, Ipswich, United Kingdom

4 Institute of Health and Wellbeing, University of Suffolk, Ipswich, United Kingdom

This umbrella review aimed to analyze the different variables of resistance training and their effect on hypertrophy, and to provide practical recommendations for the prescription of resistance training programs to maximize hypertrophy responses. A systematic research was conducted through of PubMed/MEDLINE, SPORTDiscus and Web of Science following the preferred reporting items for systematic reviews and meta-analyses statement guidelines. A total of 52 meta-analyses were found, of which 14 met the inclusion criteria. These studies were published between 2009 and 2020 and comprised 178 primary studies corresponding to 4,784 participants. Following a methodological quality analysis, nine meta-analyses were categorized as high quality, presenting values of 81–88%. The remaining meta-analyses were rated as moderate quality, with values between 63–75%. Based on this umbrella review, we can state that at least 10 sets per week per muscle group is optimal, that eccentric contractions seem important, very slow repetitions (≥10 s) should be avoided, and that blood flow restriction might be beneficial for some individuals. In addition, other variables as, exercise order, time of the day and type of periodization appear not to directly influence the magnitude of muscle mass gains. These findings provide valuable information for the design and configuration of the resistance training program with the aim of optimizing muscle hypertrophy.

Introduction

Hypertrophy is defined as an increase in muscular size, which can be achieved through exercise. Two main factors contribute to this physiological phenomenon such as sarcoplasmic hypertrophy (i.e., increased muscle glycogen storage) and myofibrillar hypertrophy (i.e., increased myofibril size and myofibrillar number) (Triplett and Haff, 2015 ). In this regard, resistance training is considered the gold standard for increasing muscle mass, which is based on three key variables such as mechanical stress, metabolic stress, and muscle damage (Ahtiainen et al., 2003 ). Traditionally, resistance training focused on hypertrophy is characterized by moderate load, high total volume load and short rest periods (Kraemer and Ratamess, 2005 ), although the effects of resistance programs vary depending on the manipulation of its variables (Schoenfeld and Grgic, 2017 ). Since promising effects related to the increase of muscular size on both performance and health have been previously reported (Maestroni et al., 2020 ), it seems justified to search for the most effective methods to generate hypertrophy.

Due to the strong positive relationship observed between the muscle's capacity to generate force and their cross-sectional area (CSA) (Maughan et al., 1983 ), hypertrophy is one of the main goals pursued by both professional and recreational athletes. Thus, several research studies have analyzed the effects of resistance training on hypertrophy and its subsequent force level (Hornsby et al., 2018 ). However, it is important to highlight that most team sports require high-force level, but also that the athletes must apply it in the minimum time period (Taber et al., 2016 ). Regarding this, increasing muscle mass include a positive influence on rate of force development and power, which improve sportive actions such sprinting, jumping, and change of direction ability (Keiner et al., 2014 ; Seitz et al., 2014 ; Suchomel et al., 2018 ). In addition, muscle mass is a key factor in sports disciplines where the quality and quantity of muscle development is judged, such as bodybuilding (Schoenfeld, 2010 ). Therefore, promoting hypertrophy could be a relevant strategy for improving sports performance (Andersen et al., 2000 ).

From a human health standpoint, muscle mass plays a significant role in several actions of daily life as locomotion (McLeod et al., 2016 ), so low levels of muscle mass may lead to an increased risk of several diseases (Maestroni et al., 2020 ). In this regard, resistance training and their associated hypertrophy adaptations have been shown to have health benefits such as reducing body fat, increasing metabolic rate, lowering blood pressure and cardiovascular demands on exercise, improving blood lipid profile, glucose tolerance and insulin sensitivity, a reduction in the risk of suffering from type II diabetes, an improvement in mobility and functional capacity, an increase in strength, muscle and bone mass, and an increase in related factors with quality of life (Wolfe, 2006 ; Maestroni et al., 2020 ). Specifically, Balachandran et al. ( 2014 ) applied a hypertrophy-oriented resistance program (3 sets of 10–12 repetitions using 70% of their one-repetition maximum and 1–2 min recovery) with sarcopenic obese adults during 15 weeks obtaining improvements in functional capability and power, as well as a reduction in fat mass. On the other hand, Kadoglou et al. ( 2012 ) observed significant improvements in glycemic control, insulin sensitivity and triglycerides after the application of a hypertrophy training program (2–3 sets of 8–10 repetitions using 60–80% of the one-repetition maximum and 1–2 min recovery) in adults with type 2 diabetes mellitus. For all these aforementioned benefits, a comprehensive and controlled increase in muscle mass seems to be recommended for anyone, regardless of their age or fitness level.

Muscle hypertrophy adaptations can be obtained through several resistance training programs (Lixandrão et al., 2015 ; Radaelli et al., 2015 ; Fink et al., 2016 ). However, there is no well-established consensus on how resistance training variables should be manipulated to optimize muscle growth, so an umbrella review on this topic is necessary. An umbrella review is characterized by a unique criterion for the selection of scientific evidence, which only considers for inclusion the higher standard of evidence such as systematic reviews and meta-analyses (Aromataris et al., 2015 ). This approach offers the opportunity to compare and discuss findings of different review papers—that can be summarized in a single review. Thus, the aims of this review were, firstly, to analyze the current and high-quality scientific literature (i.e., meta-analysis) on the manipulation of different variables of resistance training and their effect on hypertrophy responses, and, secondly, to provide practical recommendations for the prescription of resistance training programs to maximize hypertrophy responses.

Umbrella Review Design

The present umbrella review was carried out following the guidelines set forth by the working group of Aromataris et al. ( 2015 ) and followed the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) statement guidelines (Page et al., 2021 ).

Search Strategy

For this research, the following database were included: PubMed/MEDLINE, SPORTDiscus and Web of Science. Likewise, ResearchGate was used as a source of complementary information. The search syntax included the following keywords coupled with Boolean operators: “meta-analysis” AND (“resistance training” OR “resistance exercise” OR “strength training” OR “strength exercise” OR “strengthening exercise” OR “weight lifting” OR “weight training” OR “blood flow restriction” OR “blood-flow restricted” OR “blood flow restricted” OR “blood restriction” OR BFR OR hypoxia OR “muscle actions”) AND ((hypertrophy OR muscles OR CSA OR “cross sectional area” OR “cross-sectional area” OR growth OR “muscle size” OR “muscle thickness” OR “lean body mass” OR LBM OR “fat free mass” OR “fat-free mass” OR “skeletal muscle” OR “muscle fibers” OR bodybuilding OR “body building” OR “muscle gain” OR “muscular volume” OR “body composition” OR “muscular adaptations” OR “hypertrophic effects”) AND (volume OR frequency OR frequencies OR sets OR multiple OR single OR tempo OR velocity OR speed OR duration OR repetitions OR order OR “split training” OR “total body training” OR “split routine” OR “split weight training” OR ((training OR light OR low OR “low-” OR “high-”) AND load) OR “low-load” OR “high-load” OR intensity OR eccentric OR concentric OR shortening OR lengthening OR “contraction mode” OR “time-of-day” OR “time of day” OR “diurnal fluctuations” OR “circadian variation” OR “circadian rhythms” OR program OR programs). A secondary search was performed based on the screening of the reference lists of the selected meta-analyses. The last and definitive search was conducted on 27th November 2021. Two authors (RBV and JR) independently screened the title and abstract of each reference to locate potentially relevant studies and reviewed them in detail to identify articles that met the inclusion criteria. Any discrepancies between the authors in the selection process were solved in consultation with a third reviewer (DC).

Inclusion Criteria

Meta-analyses published in English whose aim was to analyze the effect of manipulating different variables of resistance training in muscle hypertrophy adaptations were included in this umbrella review. Following to the Participant-Intervention-Comparison-Outcome (PICO) process for evidence-based practice (Schardt et al., 2007 ), the subsequent inclusion criteria were applied:

• a) Participants: Male and/or female healthy and physically active practitioners. Studies focused on specific age-populations as children or elderly participants were excluded.
• b) Interventions: Resistance training programs with traditional materials (i.e., free weights and weight stack machines).
• c) Comparison group: Usual training (no additional training).
• d) Outcome measures: Muscle mass, CSA, lean body mass, muscle girth, muscle thickness, fat-free mass, muscle fibers and muscle volume.

Methodological Quality Analysis

The methodological quality of the included meta-analyses was assessed through the Assessing the Methodological Quality of Systematic Reviews 2 (AMSTAR 2) checklist, which is considered as a reliable and valid tool to evaluate the risk of bias (Shea et al., 2017 ). AMSTAR 2 is composed by 16 different items, which were answered with a “yes”, “no”, “cannot answer” or “not applicable” and only positive answers (i.e., “yes”) allow to sum 1 point. Meta-analyses were classified as high quality (at least 80% of the items were satisfied), moderate quality (between 40 and 80% of the items were satisfied) or low quality (<40% of the items were satisfied) attending to the obtained score in the AMSTAR 2 checklist.

Quality of the Evidence Evaluation

The quality of the evidence was evaluated using the modified Grading of Recommendations Assessment, Development and Evaluation (GRADE) principles (Guyatt et al., 2011 ). In this sense, systematic reviews were classified as high (i.e., at least two high-quality primary studies), moderate (i.e., at least one high quality primary study or at least two moderate-quality primary studies), low (i.e., only moderate-quality primary studies and/or inconsistent results in the primary studies) or very low (i.e., no medium to high quality systematic review identified on this topic). If the quality of the primary studies was not assessed, the systematic review must be classified as “no evidence from systematic review”.

Study Coding and Data Extraction

The following moderator variables were extracted from the included reviews: (a) authors and year of publication, (b) resistance training variable analyzed, (c) main aim of the meta-analysis, (d) number of studies/participants included in the meta-analysis, (e) mean interventions duration, (f) heterogeneity among primary studies (I 2 ), and (g) main findings or conclusions reported by the authors. Data extraction, methodological quality assessment and quality of the evidence evaluation were performed independently by two authors (RBV and JRG) and discrepancies between the authors were resolved in consultation with a third reviewer (DC).

Search Results

Figure 1 shows the flow diagram of the meta-analyses' retrieval process followed in this umbrella review. The initial search identified 55 meta-analyses, while 2 additional meta-analyses were found through the secondary search. Subsequently, 25 duplicate records were removed, and 13 meta-analyses were excluded based on their titles and/or abstracts. Nineteen meta-analyses were read in more detail (i.e., full-text) and 14 meta-analyses were included in the umbrella review (Roig et al., 2009 ; Krieger, 2010 ; Schoenfeld et al., 2015 , 2016a , 2017a , b , c , 2019a ; Slysz et al., 2016 ; Grgic et al., 2017 , 2019 ; Lixandrão et al., 2018 ; Grgic, 2020 ; Nunes et al., 2020 ).

Flow diagram of the study retrieval process.

Descriptive Characteristics of the Umbrella Review

The included meta-analyses are summarized in Table 1 . These studies were published between 2009 and 2020 and comprised 178 primary studies corresponding to 4,704 participants. The 14 selected meta-analyses were classified attending to the analyzed variable, differentiating between volume (Krieger, 2010 ; Schoenfeld et al., 2017a ), frequency (Schoenfeld et al., 2019a ), intensity (Schoenfeld et al., 2016a , 2017c ; Grgic, 2020 ), contraction type (Roig et al., 2009 ; Schoenfeld et al., 2017b ), repetition duration (Schoenfeld et al., 2015 ), exercises order (Nunes et al., 2020 ), time of day (Grgic et al., 2019 ), periodization followed (Grgic et al., 2017 ) and blood-flow restriction (Slysz et al., 2016 ; Lixandrão et al., 2018 ).

Summary of meta-analyses that investigated the effects of modify resistance training variables on hypertrophy.

NR, non-reported; 1RM, one repetition maximum; BFR, blow flood restriction .

Methodological Quality Assessment and Quality of the Evidence Evaluation

The methodological quality of the 14 included meta-analyses is presented in Table 2 . Nine meta-analyses were categorized as high quality, presenting values of 81 and 88% (i.e., 13 items satisfied) (Schoenfeld et al., 2015 , 2017a , b , 2019a ; Grgic et al., 2017 , 2019 ; Lixandrão et al., 2018 ; Nunes et al., 2020 ). The remaining meta-analyses were rated as moderate quality, with values between 63 and 75% (i.e., from 10 to 12 items satisfied) (Roig et al., 2009 ; Krieger, 2010 ; Schoenfeld et al., 2016a , 2017c ; Slysz et al., 2016 ; Grgic, 2020 ). According to GRADE, 8 meta-analyses were based on high-quality primary studies (i.e., high GRADE) (Roig et al., 2009 ; Slysz et al., 2016 ; Grgic et al., 2017 , 2019 ; Schoenfeld et al., 2017c ; Lixandrão et al., 2018 ; Grgic, 2020 ; Nunes et al., 2020 ) while the other 7 meta-analyses did not presented information regarding to quality (Krieger, 2010 ; Schoenfeld et al., 2015 , 2016a , 2017a , b , 2019a ).

Overall results of the AMSTAR 2 checklist.

AMSTAR 2, Assessing the Methodological Quality of Systematic Reviews 2; NEFSR, No evidence from systematic review .

The main aims of this review were, firstly, to analyze the different variables of resistance training and their effect on hypertrophy responses, and secondly, to provide practical recommendations for the prescription of resistance training programs to maximize hypertrophy responses. Based on the 14 meta-analyses and the 178 primary studies included in our umbrella review, we can conclude that the variables of volume, frequency, intensity, contraction type, repetition duration, and the application of the restriction of blood flow can generate hypertrophy adaptations in healthy subjects. Conversely, other variables such as exercise order, time of the day and type of periodization appear not to directly influence the magnitude of muscle mass gains, however further research is necessary to clarify their capability to stimulate hypertrophy. The findings reported in this umbrella review provide valuable information for the design and configuration of resistance training programs aiming at optimizing muscle hypertrophy.

Volume is commonly defined as the total amount of work performed (Schoenfeld and Grgic, 2017 ) and can be expressed as the total number of sets/repetition per exercise (Wernbom et al., 2007 ; Schoenfeld et al., 2017a ) or the total number of repetitions multiplied by the amount of weight used in an exercise across sets (Schoenfeld et al., 2016b ). This variable has received a great deal of attention with respect to enhancing muscle hypertrophy (Schoenfeld and Grgic, 2017 ), since it has been traditionally assumed that prescribing high-volume during resistance training programs will produce greater gains in muscle mass (McCall et al., 1999 ). This statement is supported by the fact that, when the rest of the variables remain constant, increases in volume will necessarily increase the overall time-under-tension, which has been proposed as an important driver of anabolism (Burd et al., 2012 ). However, it is still not clear if there is a real dose-response relationship for this variable and if there is a cut-off point from which, even if the volume increases, the muscle hypertrophy does not increase. In this regard, Krieger ( 2010 ) performed a meta-analysis in order to compare the effects on hypertrophy response between the use of one and multiple sets per exercise and to establish a dose-response relationship between training volume and hypertrophy adaptations. This author found that performing multiple sets (2–3 sets) entails 40% more hypertrophy compared to a single set (Krieger, 2010 ). Regarding the analysis of the dose-response relationship, the results of this meta-analysis (Krieger, 2010 ) reported significant differences in muscle mass gains when 2-3 sets compared to 1 set were performed, while no differences were observed when comparing volumes of 2–3 sets vs. 4–6 sets. This could be due to the theoretically increasing of protein synthesis with increased volume up (Spangenburg, 2009 ) to a point (Kumar et al., 2009 ), from which this production remains stable—limiting greater gains in muscle mass. According to the previous study, Schoenfeld et al. ( 2017a ) observed a graded dose-response relationship between resistance training weekly volume and muscle growth. Specifically, these authors established that low-volume protocols ( ≤ 4 weekly sets per muscle group) could be enough to get substantial gains in muscle hypertrophy, which is valuable information to those for which the conservation of energy is an ongoing concern or those with a reduced time availability. However, they also observed that at least 10 weekly sets per muscle group is necessary to maximize increases in muscle mass (Schoenfeld et al., 2017a ). Some authors hypothesized that the repeated application of high-volume stimulus during resistance training sessions maximizes the anabolic responses (higher protein synthesis) due to the greater metabolic stress generated (Schoenfeld, 2013 ). Finally, these authors also refer to the existence of a hypertrophic adaptations plateau, advising that training above this level could generate overtraining. Although resistance training volume seems to present a positive dose-response relationship, further research is needed to clarify the level over which there is a plateau, which is currently not well understood. These meta-analyses included in this umbrella review showed some limitations—authors highlight the scarce number of studies that included 4–6 sets per exercises as training variable, as well as the use of indirect measurement methods (e.g., BodPod) to assess the muscle gains in some of the includes studies.

Closely related to volume, frequency appears to be a key variable for hypertrophy gain, which refers to the number of resistance training sessions performed or the number of times a specific muscle group is trained in a given period of time, usually a week (Schoenfeld et al., 2016c ). To determine the effects of resistance training frequency on hypertrophic outcomes, Schoenfeld et al. ( 2019a ) observed that when volume is equated, frequency does not significantly impact muscle hypertrophy. Instead, the authors reported that a significant effect favoring higher frequencies was observed when volume was not equated. This could be due to the fact that by maintaining the volume, increasing the weekly frequency allows maintaining the intensity of the effort optimizing recovery between sessions. However, it has been observed that using high training frequencies combined with high intensities can lead to a rapid decline in performance and an increased risk of overtraining (Fry et al., 1994 ). Therefore, periodizing frequency and/or including periods of low frequency on a regular basis (i.e., tapering periods) can help to maximize hypertrophy responses and to reduce the potential for overtraining, but more research is needed to verify this hypothesis (Fry et al., 1994 ). Despite these results, training frequency can be a useful strategy to increase the overall training volume, a variable that has shown a dose-response relationship with hypertrophy (Schoenfeld et al., 2017a ). In addition, variations in inter-individual responses to training frequency has been observed, so individualization of the training program is essential to maximize the hypertrophy potential of each participant (Haff and Nimphius, 2012 ).

The main limitations observed in the review in our hands, which examined the effect of training frequency on hypertrophy, were that the direct measurements were only carried out on the thighs and arms, so the results cannot be extrapolated to other muscle groups; it was not possible to compare the effect of training frequency between multi-joint and single-joint exercises as well as the effect of participants' age on chronical adaptations.

This variable is considered one of those with the greatest effect on hypertrophy responses (Fry, 2004 ). In this regard, each percentage of the 1RM is related to a certain number of maximum repetitions to be performed (Brzycki, 1993 ), traditionally categorized into low (<30% 1RM, >20 reps), moderate (30–70% 1RM, 11–20 reps) and high (>70% 1RM, <11 reps) ranges (Soriano et al., 2015 , 2017 ). Consequently, each percentage of 1RM is associated with a different energy system and fatigue level (Sánchez-Medina and González-Badillo, 2011 ), impacting the extent of the hypertrophic response (Schoenfeld, 2010 ). Traditionally, training using high loads with a moderate number of repetitions (i.e., 80% 1RM, 8–10 reps) has been considered as a key strategy to optimize the muscle gains (Kerksick et al., 2009 ), based on the existence of an intensity threshold from which the increase in metabolic stress improves the hypertrophy response, allowing the recruitment of high-threshold motor units, which is not possible with the high repetition range (Schoenfeld, 2010 ). However, there is a lack of evidence to objectively establish the balance between external load, metabolic stress and hypertrophy responses. Schoenfeld et al. ( 2016a ) performed a meta-analysis aiming to compare the effects of low- vs. high-load training in enhancing post-exercise muscular hypertrophy, who observed that resistance training programs using loads < 60% 1RM allows to achieve hypertrophy levels similar to those achieved with high loads (≥65% 1 RM) in untrained individuals, although they observed a trend toward greater hypertrophy using high loads (difference = 0.43 ± 0.24; CI: −0.05, 0.92; p = 0.076), (Schoenfeld et al., 2016a ) which supports the established guidelines for hypertrophy training (loads > 65% 1RM) (Kraemer and Ratamess, 2004 ). These similar hypertrophy responses reported in this review could be due to several factors such as the training level of the participants involved in the studies, the length of the training process, the type of exercise utilized, rest interval, and training frequency. In a second meta-analysis, Schoenfeld et al. ( 2017c ) observed similar hypertrophy changes after the use of high or low loads when muscle failure was reached. Conversely to the first reported meta-analysis, this study did not observe a superior trend toward the use of high loads. These authors suggest that training with low loads implies a higher level of discomfort, although this did not imply a lower adherence to it compared to that reported in programs with high loads. Finally, Grgic ( 2020 ) conducted a new meta-analysis on this topic and observed non-significant differences in hypertrophy when comparing the effects of low-loads vs. high-loads (performed to momentary muscular failure) in both type I and type II muscle fibers. Additionally, this author reported a 95% confidence and prediction intervals very wide, so there is a clear need for future research on this topic. These results suggest that the selection of the load to use within a strength training program whose objective is to increase muscle mass should be made based on individual criteria (e.g., training status of the participants, length of the training process).

A limitation of these meta-analyses (Schoenfeld et al., 2016a , 2017c ) is the level of the participants (untrained individuals with minimal research on trained individuals) which difficult to extrapolate the results to trained athletes. In addition, few participants were involved in the included studies and the length of the protocols in some studies was a bit reduced.

Contraction Type

Traditionally, it has been assumed that eccentric contractions promote greater gains in muscle mass compared to concentric contractions (Hortobágyi et al., 2000 ), based on the idea that the mechanical stress placed on the eccentrically contracted muscles triggers a progressive activation of genes responsible for cellular growth and development, which is not possible by concentric or isometric actions (Chen et al., 2002 ; Barash et al., 2004 ). Additionally, some authors have suggested that eccentric actions promote a more rapid protein synthetic response and greater increases in anabolic signaling (Franchi et al., 2014 ), generated by the result of the increase muscle damage (Schoenfeld, 2012 ). To get a more comprehensive knowledge about the superiority of eccentric contractions compared to concentric contractions in muscle gains, Roig et al. ( 2009 ) observed that eccentric exercise is more effective than concentric exercise in increasing muscle girth mainly due to the higher absolute loads imposed during eccentric contractions. However, these authors also indicated that concentric training performed separately can promote increases in muscle mass. Schoenfeld et al. ( 2017b ) performed a meta-analysis and confirmed the advantage of eccentric contractions for increasing hypertrophy, although this advantage was relatively small (eccentric training 10% vs. concentric 6.8%). These differences could be explained because of the higher force and mechanic load generated during eccentric training compared to concentric when the same repetitions number is performed (Schoenfeld et al., 2017b ). However, when mechanical work was equaled, the results obtained were inconclusive (Hawkins et al., 1999 ; Moore et al., 2012 ). Additionally, Schoenfeld et al. ( 2017b ) also observed that concentric contractions induced hypertrophy gains in the middle portion of the muscle, while eccentric contractions have a greater effect on the distal portions, possibly due to localized muscle damage along the fiber produced by non-uniform muscle activation of eccentric contractions. Due to the different responses of both contractions, it seems appropriate to combine both types to optimize the hypertrophy response (e.g., using technologies that allow this) (Beato and dello Iacono, 2020 ). Finally, these authors found that eccentric training produced greater hypertrophy of type II fibers than concentric, which could be explained because eccentric contractions preferentially recruit high-threshold motor units, which contain more type II fibers (Beato and dello Iacono, 2020 ). However, the mechanism by which such a fiber type preference exists is not clear.

The comparison between adaptations on hypertrophy caused by concentric and eccentric contractions have been limited by the difficulty of isolating them from human movement, which implies a cyclical repetition of both types of contraction; the uncertainty to know the intensity implied by an external load during an eccentric contraction; and the specificity of resistance training regarding speed and mode of contraction (Roig et al., 2009 ). Therefore, it seems necessary to delve into the possible relationship between the effects on hypertrophy and the type of contraction, differentiating between body hemispheres, different muscle regions, the role of induced muscle damage in the increase in hypertrophy, the influence of the angle of pennation and the length of the fascicle and the comparison between types of contractions equating mechanic load (Roig et al., 2009 ; Schoenfeld et al., 2017b ).

Repetition Duration

Training with loads lower than 80–85% 1RM allows the trainee to voluntarily modify the tempo of the lift (Bamman et al., 2001 ), an action that reduces the velocity of the lift by increasing the mechanical tension manifested by the muscle (Westcott et al., 2001 ), thus promoting a greater hypertrophy response (Schoenfeld et al., 2015 ). In this regard, Schoenfeld et al. ( 2015 ) conducted a meta-analysis and observed similar gains in hypertrophy when training with repetition durations ranging from 0.5 to 8 s (to concentric muscular failure). However, it was also observed that training at volitionally very slow durations (10 s per repetition) is inferior from a hypertrophy standpoint. The authors speculate on the existence of a possible threshold velocity below which the hypertrophy response is impaired, since it could not be a suitable stimulus to recruit all motor units of a muscle—mainly high-threshold motor units (Keogh et al., 1999 ). Nevertheless, the training programs analyzed in this study were performed until concentric failure, which implies a progressive increase in fatigue along the set, reducing the motor unit recruitment thresholds, thereby enhancing muscle recruitment (Mitchell et al., 2012 ). From a practical perspective, a wide range of repetition durations can be used to stimulate hypertrophy, however, very slow repetitions (around 10 s) should be avoided. Considering that the evidence on this topic is limited, future studies on the effects of variation in the duration of repetitions must be performed in different contexts.

Exercise Order

Multi-joint exercises are those that recruit one or more large muscle groups involving two or more main joints, while single-joint exercises are those that involve smaller muscle groups involving a single main joint (Haff and Nimphius, 2012 ). Specifically, multi-joint exercises generate a significant stabilization of the body, involving numerous muscles that could not be stimulated by single-joint movements (Schoenfeld, 2010 ). However, the biarticular muscles do not receive sufficient hypertrophy stimulation in multi-joint exercises since, during their execution, these muscles maintain a relatively constant length. Therefore, single-joint exercises are necessary to achieve a better length-tension relationship (greater mechanical tension following the length-tension principle) and a greater electromyography activity (a possible greater motor unit recruitment) (Schoenfeld et al., 2019b ). In this sense, to know the best organization of these type of exercises within a resistance training session seems to be a key factor in order to optimize the muscle mass gains. Nunes et al. ( 2020 ) conducted a meta-analysis to analyze the effects of exercise order on muscular hypertrophy and the obtained results indicated similar hypertrophy responses regardless of exercise order, although authors claimed that this finding should be viewed with caution. In the included studies in which model B ultrasounds were used, measurements were taken in muscles that were not the object of the investigation, that is, hypertrophy measurements were performed on muscles that were agonists in the single-joint but synergists in the multi-joint exercises (e.g., biceps brachia in a bicep curl and in a vertical pull). In the studies that used indirect measurement methods, no significant differences were found either, but these methods have low sensitivity to identify subtle hypertrophy changes (Haun et al., 2019 ). Currently, we do not have enough evidence to state proper guidelines and, therefore, more research seems necessary, including analysis of different exercise orders with exercises on the same target muscle in which it also acts as the main agonist, and not only as a synergist, as well as using direct measurement methods on specific muscle regions (which have greater sensitivity).

Time of Day

Human motor performance varies depending on the time of day (Drust et al., 2005 ). The time of day in which maximum performance is reached is called acrophase, which is around 6:00 p.m. attending resistance training (Guette et al., 2005 ). In this regard, Grgic et al. ( 2019 ) concluded that the hypertrophy adaptations were similar regardless of the time of day the training sessions were located. These findings could be partially explained by the similar levels of p70S6K phosphorylation observed after strength training performed in the morning or afternoon (Mayhew et al., 2011 ). These results suggest that the time of day for strength and hypertrophy training should be based on personal preference, although more research appears to be needed to really verify if differences exist between training in the morning vs. evening hours. Future studies should consider the assessment of CSA at the muscle fiber level and individual responses to resistance training at different times of the day based on chronotype (morning or evening) and habitual sleep cycles.

Periodization

Triplett and Haff ( 2017 ) define periodization as “ the logical and systematic process of sequencing and integrating training interventions in order to reach peak performance at appropriate times .” Two of the most used periodization models in resistance training are the linear periodization model and the non-linear or undulating model. To compare the effects of these periodization models, Grgic et al. ( 2017 ) conducted a meta-analysis and found that at the same training volume, no significant differences were observed, although it cannot be guaranteed that the same occurs with other forms of periodization. With these results, the importance of training volume in modulating the hypertrophy response was once again confirmed (Schoenfeld et al., 2017a ). For this reason, linear periodization does not seem to be the most appropriate since it ends with the minimum volume and it is suggested that the inverse linear periodization model, in which the intensity is decreased and the volume increases, seems to be a better alternative since the maximum volume would be at the end of the macrocycle (Prestes and Lima, 2009 ). Even in trained subjects, who tend to present an attenuated response to training, significant improvements in hypertrophy have been observed without having applied any periodization model, simply with an adequate progressive overload. This leads to questioning the need to implement periodization models in resistance training programs (Morton et al., 2016 ). A possible consideration when establishing a periodization model can be the motivational factor in order to ensure adherence to training, being linear periodization more suitable for individuals who want to record weekly or monthly progress; while undulating periodization might be recommended for those who enjoy more the variety of training or because they have different training aims (Grgic et al., 2017 ).

Blood Flow Restriction

To optimize hypertrophy, different strategies related to resistance training have been implemented, highlighting the blow flood restriction (Slysz et al., 2016 ). This method is based on the decrease blood flow to a muscle by application of an external constricting device, such as a blood pressure cuff or tourniquet, to provide mechanical compression of the underlying vasculature (Slysz et al., 2016 ). In this regard, in with the aim to increase the knowledge about this technique, Slysz et al. ( 2016 ) assessed the effectiveness of blow flood restriction exercise on muscle hypertrophy compared to traditional resistance training. These authors observed that the addition of blow flood restriction to dynamic exercise training is effective for augmenting changes in muscle size, mainly when training programs last at least 8 weeks and cuff pressures > 150 mmHg are used. Accordingly, Lixandrão et al. ( 2018 ) demonstrate similar muscle gains for high-load as compared with low-load resistance training associated with blow flood restriction techniques. Even though occlusion pressure, which is highly dependent on the width of the cuff, has been considered an important variable in blow flood restriction due to its ability to modulate muscle adaptations, the results obtained show total independent of the absolute occlusion pressure and the width of the cuff used (Lixandrão et al., 2018 ). However, authors stated that the occlusion pressure has been shown to have a direct relationship with the perception of effort and suggest that blow flood restriction with low pressures is perceived as more comfortable and less physically demanding, being especially useful in individuals with low tolerance to physical stress. Future research on a possible preference of the blow flood restriction stimulus over type I fibers seems to be interesting.

Methodological Quality of the Included Meta-Analysis

As assessed using the AMSTAR 2 checklist, the included meta-analyses are classified as moderate or high methodological quality. Despite the acceptable overall quality of the included meta-analyses, we noted, regarding to the GRADE quality assessment, that 6 out 14 meta-analyses did not reported information about the quality of the primary studies analyzed. This methodological issue shows the necessity of establishing clear and specific methodological guidelines to apply in resistance training meta-analyses to increase the robustness of the findings.

Conclusions

Based on the available meta-analyses, it has been observed that volume, frequency, intensity, contraction type, repetition duration and the application of the restriction of blood flow conditioning hypertrophy adaptations in healthy subjects, being volume the only resistance training variable for which a dose-response relationship with hypertrophy adaptations has been observed. Conversely, other variables as, exercise order, time of the day and type of periodization appear not to directly influence the magnitude of muscle mass gains. These findings provide valuable information for the design and configuration of the resistance training program with the aim of optimizing muscle hypertrophy.

Practical Applications

From the existing literature some recommendations must be considered when resistance training program focused on muscle mass gains are prescribed:

• a) Volume : research has reported a graded dose-response relationship between resistance training weekly volume and muscle growth. Therefore, it would be recommended to prescribe 2–3 sets per exercise, covering at least 10 weekly sets for each muscle group, while greater weekly volume does not seem to offer additional hypertrophy benefits.
• b) Frequency : although the modification of this variable does not directly influence hypertrophy gains, significant effect favoring higher frequencies was observed when volume was not equated, therefore training frequency can be used as a tool to modify the overall weekly training volume.
• c) Intensity : the choice of light or heavy loads can be made depending on the characteristics of the subject, although always reaching or close to failure. It is appropriate to prescribe variations in the magnitude of the load (<60% 1RM and >60% 1RM), however higher load seem to offer greater adaptations.
• d) Contraction type : it seems appropriate to combine both concentric and eccentric contractions to optimize hypertrophy response, however, it seems that eccentric contractions may offer some additional advantages compared to concentric.
• e) Repetition duration : a wide range of repetition duration seems to be appropriated to stimulate hypertrophic adaptations such as 0.5–8 s, instead, longer duration (very slow movement speed) is counterproductive, therefore it should avoid extending the repetition duration beyond 10 s.
• f) Exercises order : for the modulation of this variable, personal preferences or specific objectives must be addressed, such as deliberately overloading a specific muscle group. Currently, we do not have enough evidence to state proper guidelines and, therefore, more research seems necessary.
• g) Time of day : for the modulation of this variable, personal preferences must be addressed since no evidence in favor of a specific time of day (morning vs. evening hours) have been found on hypertrophy adaptations.
• h) Periodization : individual preferences must be considered when choosing the periodization model to use, but always respecting the training volume and progressive overload.
• Blood flow restriction : it seems appropriate to use this technique in widely experienced subjects or in those who cannot use heavy loads (i.e., injured athletes).

Author Contributions

RB-V and JR-G conceived the research idea, collected the included studies, and prepared the manuscript. All authors critically revised the manuscript, read, and approved the final version.

Conflict of Interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Publisher's Note

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.

• Ahtiainen J. P., Pakarinen A., Alen M., Kraemer W. J., Häkkinen K. (2003). Muscle hypertrophy, hormonal adaptations and strength development during strength training in strength-trained and untrained men . Eur. J. Appl. Physiol . 89 , 555–563. 10.1007/s00421-003-0833-3 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Andersen J. L., Schjerling P., Saltin B. (2000). Muscle, genes and athletic performance . Sci. Am . 283 , 48–55. 10.1038/scientificamerican0900-48 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Aromataris E., Fernandez R., Godfrey C. M., Holly C., Khalil H., Tungpunkom P. (2015). Summarizing systematic reviews: methodological development, conduct and reporting of an umbrella review approach . Int. J. Evid. Based Healthcare 13 , 132–140. 10.1097/XEB.0000000000000055 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Balachandran A., Krawczyk S. N., Potiaumpai M., Signorile J. F. (2014). High-speed circuit training vs hypertrophy training to improve physical function in sarcopenic obese adults: a randomized controlled trial . Exp. Gerontol . 60 , 64–71. 10.1016/j.exger.2014.09.016 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Bamman M. M., Shipp J. R., Jiang J., Gower B. A., Hunter G. R., Goodman A. (2001). Mechanical load increases muscle IGF-I and androgen receptor mRNA concentrations in humans . Am. J. Physiol. Endocrinol. Metabol . 280 , E383–E3890. 10.1152/ajpendo.2001.280.3.E383 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Barash I. A., Mathew L., Ryan A. F., Chen J., Lieber R. L. (2004). Rapid muscle-specific gene expression changes after a single bout of eccentric contractions in the mouse . Cell Physiol . 286 , C355–364. 10.1152/ajpcell.00211.2003 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Beato M., dello Iacono A. (2020). Implementing flywheel (isoinertial) exercise in strength training: current evidence, practical recommendations, and future directions . Front. Physiol . 11 , 569. 10.3389/fphys.2020.00569 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Brzycki M. (1993). Strength testing—predicting a one-rep max from reps-to-fatigue . J. Phys. Ed. Recr. Danc . 64 , 88–90. 10.1080/07303084.1993.10606684 [ CrossRef ] [ Google Scholar ]
• Burd N. A., Andrews R. J., West D. W. D., Little J. P., Cochran A. J. R., Hector A. J. (2012). Muscle time under tension during resistance exercise stimulates differential muscle protein sub-fractional synthetic responses in men . J. Physiol. 590 , 351–362. 10.1113/jphysiol.2011.221200 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Chen Y. W., Nader G. A., Baar K. R., Fedele M. J., Hoffman E. P., Esser K. A. (2002). Response of rat muscle to acute resistance exercise defined by transcriptional and translational profiling . J. Physiol. 545 , 27–41. 10.1113/jphysiol.2002.021220 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Drust B., Waterhouse J., Atkinson G., Edwards B., Reilly T. (2005). Circadian rhythms in sports performance—an update . Chronobiol. Int . 22 , 21–44. 10.1081/CBI-200041039 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Fink J., Kikuchi N., Yoshida S., Terada K., Nakazato K. (2016). Impact of high versus low fixed loads and non-linear training loads on muscle hypertrophy, strength and force development . Springerplus 5 , 698. 10.1186/s40064-016-2333-z [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Franchi M. V., Atherton P. J., Reeves N. D., Flück M., Williams J., Mitchell W. K. (2014). Architectural, functional and molecular responses to concentric and eccentric loading in human skeletal muscle . Acta Physiol . 210 , 642–654. 10.1111/apha.12225 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Fry A. C. (2004). The role of resistance exercise intensity on muscle fibre adaptations . Sports Med . 34 , 663–679. 10.2165/00007256-200434100-00004 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Fry A. C., Kraemer W. J., Van Borselen F., Lynch J. M., Marsit J.L., Roy E.P., et al.. (1994). Performance decrements with high-intensity resistance exercise overtraining . Med. Sci. Sports Exerc . 26 , 1165–1173. 10.1249/00005768-199409000-00015 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Grgic J. (2020). The effects of low-load vs. high-load resistance training on muscle fiber hypertrophy: a meta-analysis . J. Hum. Kinet . 74 , 51–58. 10.2478/hukin-2020-0013 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Grgic J., Lazinica B., Garofolini A., Schoenfeld B. J., Saner N. J., Mikulic P. (2019). The effects of time of day-specific resistance training on adaptations in skeletal muscle hypertrophy and muscle strength: a systematic review and meta-analysis . Chronobiol. Int . 36 , 449–460. 10.1080/07420528.2019.1567524 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Grgic J., Mikulic P., Podnar H., Pedisic Z. (2017). Effects of linear and daily undulating periodized resistance training programs on measures of muscle hypertrophy: a systematic review and meta-analysis . PeerJ 5 , e3695. 10.7717/peerj.3695 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Guette M., Gondin J., Martin A. (2005). Time-of-day effect on the torque and neuromuscular properties of dominant and non-dominant quadriceps femoris . Chronobiol. Int . 22 , 541–558. 10.1081/CBI-200062407 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Guyatt G., Oxman A. D., Akl E. A., Kunz R., Vist G., Brozek J. (2011). GRADE guidelines: 1. Introduction - GRADE evidence profiles and summary of findings tables . J. Clin. Epidemiol . 64 , 383–394. 10.1016/j.jclinepi.2010.04.026 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Haff G. G., Nimphius S. (2012). Training principles for power . Strength Cond. J . 34 , 2–12. 10.1519/SSC.0b013e31826db467 [ CrossRef ] [ Google Scholar ]
• Haun C. T., Vann C. G., Roberts B. M., Vigotsky A. D., Schoenfeld B. J., Roberts M. D. (2019). A critical evaluation of the biological construct skeletal muscle hypertrophy: size matters but so does the measurement . Front. Physiol . 10 , 247. 10.3389/fphys.2019.00247 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Hawkins S. A., Schroeder E. T., Wiswell R. A., Jaque S. V., Marcell T. J., Costa K. (1999). Eccentric muscle action increases site-specific osteogenic response . Med. Sci. Sports Exerc . 31 , 1287–1292. 10.1097/00005768-199909000-00009 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Hornsby W. G., Gentles J. A., Haff G. G., Stone M. H., Buckner S. L., Dankel S. J. (2018). What is the impact of muscle hypertrophy on strength and sport performance? Strength Cond. J . 40 , 99–111. 10.1519/SSC.0000000000000432 [ CrossRef ] [ Google Scholar ]
• Hortobágyi T., Dempsey L., Fraser D., Zheng D., Hamilton G., Lambert J. (2000). Changes in muscle strength, muscle fibre size and myofibrillar gene expression after immobilization and retraining in humans . J. Physiol . 524 , 293–304. 10.1111/j.1469-7793.2000.00293.x [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Kadoglou N. P. E., Fotiadis G., Athanasiadou Z., Vitta I., Lampropoulos S., Vrabas I. S. (2012). The effects of resistance training on ApoB/ApoA-I ratio, Lp(a) and inflammatory markers in patients with type 2 diabetes . Endocrine 42 , 561–569. 10.1007/s12020-012-9650-y [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Keiner M., Sander A., Wirth K., Schmidtbleicher D. (2014). Long-term strength training effects on change-of-direction sprint performance . J. Strength Cond. Res . 28 , 223–231. 10.1519/JSC.0b013e318295644b [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Keogh J. W. L., Wilson G. J., Weatherby R. P. (1999). A cross-sectional comparison of different resistance training techniques in the bench press . J. Strength Cond. Res . 13 , 247–258. 10.1519/00124278-199908000-00012 [ CrossRef ] [ Google Scholar ]
• Kerksick C. M., Wilborn C. D., Campbell B. I., Roberts M. D., Rasmussen C. J., Greenwood M. (2009). Early-phase adaptations to a split-body, linear periodization resistance training program in college-aged and middle-aged men . J. Strength Cond. Res . 23 , 962–971. 10.1519/JSC.0b013e3181a00baf [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Kraemer W. J., Ratamess N. A. (2004). Fundamentals of resistance training: progression and exercise prescription . Med. Sci. Sports Exerc . 36 , 674–688. 10.1249/01.MSS.0000121945.36635.61 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Kraemer W. J., Ratamess N. A. (2005). Hormonal responses and adaptations to resistance exercise and training . Sports Med . 35 , 339–361. 10.2165/00007256-200535040-00004 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Krieger J. W. (2010). Single vs. multiple sets of resistance exercise for muscle hypertrophy: a meta-analysis . J. Strength Cond. Res . 24 , 1150–1159. 10.1519/JSC.0b013e3181d4d436 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Kumar V., Selby A., Rankin D., Patel R., Atherton P., Hildebrandt W. (2009). Age-related differences in the dose-response relationship of muscle protein synthesis to resistance exercise in young and old men . J. Physiol . 587 , 211–217. 10.1113/jphysiol.2008.164483 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Lixandrão M. E., Ugrinowitsch C., Berton R., Vechin F. C., Conceição M. S., Damas F. (2018). Magnitude of muscle strength and mass adaptations between high-load resistance training versus low-load resistance training associated with blood-flow restriction: a systematic review and meta-analysis . Sports Med . 48 , 361–378. 10.1007/s40279-017-0795-y [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Lixandrão M. E., Ugrinowitsch C., Laurentino G., Libardi C. A., Aihara A. Y., Cardoso F. N. (2015). Effects of exercise intensity and occlusion pressure after 12 weeks of resistance training with blood-flow restriction . Eur. J. Appl. Physiol . 115 , 2471–2480. 10.1007/s00421-015-3253-2 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Maestroni L., Read P., Bishop C., Papadopoulos K., Suchomel T. J., Comfort P. (2020). The benefits of strength training on musculoskeletal system health: practical applications for interdisciplinary care . Sports Med . 50 , 1431–1450. 10.1007/s40279-020-01309-5 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Maughan R. J., Watson J. S., Weir J. (1983). Strength and cross-sectional area of human skeletal muscle . J Physiol . 338 , 37–49. 10.1113/jphysiol.1983.sp014658 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Mayhew D. L., Hornberger T. A., Lincoln H. C., Bamman M. M. (2011). Eukaryotic initiation factor 2B epsilon induces cap-dependent translation and skeletal muscle hypertrophy . J. Physiol . 589 , 3023–3037. 10.1113/jphysiol.2010.202432 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• McCall G.E., Byrnes W.C., Fleck S.J., Dickinson A., Kraemer W.J. (1999). Acute and chronic hormonal responses to resistance training designed to promote muscle hypertrophy . Can. J. Appl. Physiol . 24 , 96–107. 10.1139/h99-009 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• McLeod M., Breen L., Hamilton D.L., Philp A. (2016). Live strong and prosper: the importance of skeletal muscle strength for healthy ageing . Biogerontology 17 , 497–510. 10.1007/s10522-015-9631-7 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Mitchell C. J., Churchward-Venne T. A., West D. W. D., Burd N. A., Breen L., Baker S. K. (2012). Resistance exercise load does not determine training-mediated hypertrophic gains in young men . J. Appl. Physiol . 113 , 71–77. 10.1152/japplphysiol.00307.2012 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Moore D. R., Young M., Phillips S. M. (2012). Similar increases in muscle size and strength in young men after training with maximal shortening or lengthening contractions when matched for total work . Eur. J. Appl. Physiol . 112 , 1587–1592. 10.1007/s00421-011-2078-x [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Morton R. W., Oikawa S. Y., Wavell C. G., Mazara N., McGlory C., Quadrilatero J., et al.. (2016). Neither load nor systemic hormones determine resistance training-mediated hypertrophy or strength gains in resistance-trained young men . J. Appl. Physiol . 121 , 129–138. 10.1152/japplphysiol.00154.2016 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Nunes J. P., Grgic J., Cunha P. M., Ribeiro A. S., Schoenfeld B. J., de Salles B. F., et al.. (2020). What influence does resistance exercise order have on muscular strength gains and muscle hypertrophy? A systematic review and meta-analysis . Eur. J. Sport Sci . 21 , 149–157. 10.1080/17461391.2020.1733672 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Page M. J., McKenzie J. E., Bossuyt P. M., Boutron I., Hoffmann T. C., Mulrow C. D., et al.. (2021). The PRISMA 2020 statement: an updated guideline for reporting systematic reviews . BMJ 372 , n71. 10.1136/bmj.n71 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Prestes J., Lima C. D. (2009). Comparison of linear and reverse linear periodization effects on maximal strength and body composition . J. Strength Cond. Res . 23 , 266–274. 10.1519/JSC.0b013e3181874bf3 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Radaelli R., Fleck S. J., Leite T., Leite R. D., Pinto R. S., Fernandes L. (2015). Dose-response of 1, 3, and 5 sets of resistance exercise on strength, local muscular endurance, and hypertrophy . J. Strength Cond. Res . 29 , 1349–1358. 10.1519/JSC.0000000000000758 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Roig M., O'Brien K., Kirk G., Murray R., McKinnon P., Shadgan B., et al.. (2009). The effects of eccentric versus concentric resistance training on muscle strength and mass in healthy adults: a systematic review with meta-analysis . Br. J. Sports Med . 43 , 556–568. 10.1136/bjsm.2008.051417 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Sánchez-Medina L., González-Badillo J. J. (2011). Velocity loss as an indicator of neuromuscular fatigue during resistance training . Med. Sci. Sports Exerc . 43 , 1725–1734. 10.1249/MSS.0b013e318213f880 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Schardt C., Adams M. B., Owens T., Keitz S., Fontelo P. (2007). Utilization of the PICO framework to improve searching PubMed for clinical questions . BMC Med. Inform. Decis. Mak . 7 , 16. 10.1186/1472-6947-7-16 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Schoenfeld B., Grgic J. (2017). Evidence-based guidelines for resistance training volume to maximize muscle hypertrophy . Strength Cond. J . 40 , 1. 10.1519/SSC.0000000000000363 [ CrossRef ] [ Google Scholar ]
• Schoenfeld B. J. (2010). The mechanisms of muscle hypertrophy and their application to resistance training . J. Strength Cond. Res . 24 , 2857–2872. 10.1519/JSC.0b013e3181e840f3 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Schoenfeld B. J. (2012). Does exercise-induced muscle damage play a role in skeletal muscle hypertrophy? J. Strength Cond. Res . 26 , 1441–1453. 10.1519/JSC.0b013e31824f207e [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Schoenfeld B. J. (2013). Potential mechanisms for a role of metabolic stress in hypertrophic adaptations to resistance training . Sports Med . 43 , 179–194. 10.1007/s40279-013-0017-1 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Schoenfeld B. J., Grgic J., Haun C., Itagaki T., Helms E. R. (2019b). Calculating set-volume for the limb muscles with the performance of multi-joint exercises: implications for resistance training prescription . Sports 7 , 177. 10.3390/sports7070177 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Schoenfeld B. J., Grgic J., Krieger J. (2019a). How many times per week should a muscle be trained to maximize muscle hypertrophy? A systematic review and meta-analysis of studies examining the effects of resistance training frequency . J. Sports Sci . 37 , 1286–1295. 10.1080/02640414.2018.1555906 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Schoenfeld B. J., Grgic J., Ogborn D., Krieger J. W. (2017c). Strength and hypertrophy adaptations between low- vs. high-load resistance training: a systematic review and meta-analysis . J. Strength Cond. Res . 31 , 3508–3523. 10.1519/JSC.0000000000002200 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Schoenfeld B. J., Ogborn D., Contreras B., Cappaert T., Silva Ribeiro A., Alvar B. A. (2016b). A comparison of increases in volume load over 8 weeks of low-versus high-load resistance training . Asian J. Sports Med . 7 , e29247. 10.5812/asjsm.29247 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Schoenfeld B. J., Ogborn D., Krieger J. W. (2015). Effect of repetition duration during resistance training on muscle hypertrophy: a systematic review and meta-analysis . Sports Med . 45 , 577–585. 10.1007/s40279-015-0304-0 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Schoenfeld B. J., Ogborn D., Krieger J. W. (2016c). Effects of resistance training frequency on measures of muscle hypertrophy: a systematic review and meta-analysis . Sports Med . 46 , 1689–1697. 10.1007/s40279-016-0543-8 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Schoenfeld B. J., Ogborn D., Krieger J. W. (2017a). Dose-response relationship between weekly resistance training volume and increases in muscle mass: a systematic review and meta-analysis . J. Sports Sci . 35 , 1073–1082. 10.1080/02640414.2016.1210197 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Schoenfeld B. J., Ogborn D. I., Vigotsky A. D., Franchi M. V., Krieger J. W. (2017b). Hypertrophic effects of concentric versus eccentric muscle actions: a systematic review and meta-analysis . J. Strength Cond. Res . 31 , 2599–2608. 10.1519/JSC.0000000000001983 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Schoenfeld B. J., Wilson J. M., Lowery R. P., Krieger J. W. (2016a). Muscular adaptations in low- versus high-load resistance training: A meta-analysis . Eur. J. Sport Sci . 16 , 1–10. 10.1080/17461391.2014.989922 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Seitz L. B., Reyes A., Tran T. T., de Villarreal E. S., Haff G.G. (2014). Increases in lower-body strength transfer positively to sprint performance: a systematic review with meta-analysis . Sports Med . 44 , 1693–1702. 10.1007/s40279-014-0227-1 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Shea B. J., Reeves B. C., Wells G., Thuku M., Hamel C., Moran J. (2017). AMSTAR 2: a critical appraisal tool for systematic reviews that include randomised or non-randomised studies of healthcare interventions, or both . BMJ 358 , j4008. 10.1136/bmj.j4008 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Slysz J., Stultz J., Burr J. F. (2016). The efficacy of blood flow restricted exercise: a systematic review & meta-analysis . J. Sci. Med. Sport . 19 , 669–675. 10.1016/j.jsams.2015.09.005 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Soriano M. A., Jiménez-Reyes P., Rhea M. R., Marín P. J. (2015). The optimal load for maximal power production during lower-body resistance exercises: a meta-analysis . Sports Med . 45 , 1191–1205. 10.1007/s40279-015-0341-8 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Soriano M. A., Suchomel T. J., Marín P. J. (2017). The optimal load for maximal power production during upper-body resistance exercises: a meta-analysis . Sports Med . 47 , 757–768. 10.1007/s40279-016-0626-6 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Spangenburg E. E. (2009). Changes in muscle mass with mechanical load: possible cellular mechanisms . Appl. Physiol. Nutr. Metab . 34 , 328–335. 10.1139/H09-010 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Suchomel T. J., Nimphius S., Bellon C. R., Stone M. H. (2018). The importance of muscular strength: training considerations . Sports Med . 48 , 765–785. 10.1007/s40279-018-0862-z [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Taber C., Bellon C., Abbott H., Bingham G. E. (2016). Roles of maximal strength and rate of force development in maximizing muscular power . Strength Cond. J . 38 , 71–78. 10.1519/SSC.0000000000000193 [ CrossRef ] [ Google Scholar ]
• Triplett N. T., Haff G. G. (2015). Essentials of Strength Training and Conditioning . Champaign, IL: Human Kinetics. [ Google Scholar ]
• Triplett N. T., Haff G. G. (2017). Principios del entrenamiento de la fuerza y del acondicionamiento físico . 4 a edición. Paidotribo editor. Ciudad de México: NSCA. [ Google Scholar ]
• Wernbom M., Augustsson J., Thomeé R. (2007). The influence of frequency, intensity, volume and mode of strength training on whole muscle cross-sectional area in humans . Sports Med . 37 , 225–264. 10.2165/00007256-200737030-00004 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Westcott W. L., Winett R. A., Anderson E. S., Wojcik J. R., Loud R. L. R., Cleggett E. (2001). Effects of regular and slow speed resistance training on muscle strength . J. Sports Med. Phys. Fitness . 41 , 154–158. [ PubMed ] [ Google Scholar ]
• Wolfe R. R. (2006). The underappreciated role of muscle in health and disease . Am. Clin. Nutr . 84 , 475–482. 10.1093/ajcn/84.3.475 [ PubMed ] [ CrossRef ] [ Google Scholar ]