Strength and Physique Systematic Review and Meta-Analysis Master List

Due to the significance of systematic reviews and meta-analyses, we’ve put together a list and short take-home message of many recent systematic reviews and meta-analyses so you can cut straight to the chase of the results.
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It should be obvious from the name of this site that we’re pretty into science around these parts. When we discuss a particular subject, we try to give a broad, objective overview of all the relevant studies in that area. I’d never claim we’re perfect, but that’s always our aim. However, not everyone is that scrupulous. A common tactic used by many people who aim to appear scientific while still pushing an agenda is called “cherry picking.” Cherry picking refers to discussing only research that supports your point of view, while ignoring or impugning research that disagrees with your biases. In any area of science with a lot of studies being conducted, there are going to be some studies that support one position, and other studies that support the entirely opposite position. The cynic would take that as evidence that science can’t be trusted, but it’s generally much less sinister than that. Simply due to different methodologies, different subject pools, and random chance, you should expect studies to come to differing conclusions. So, how can you avoid cherry picking, but also just avoid saying “some studies say this and some studies say that, so we really have no idea”? Systematic review and meta-analyses.

In a review article, you discuss the findings of many studies instead of primarily just reporting the results of a single study. Not all reviews are created equal, though. In systematic reviews, you follow an extensive set of guidelines to ensure you find and report the results of all of the research in a given area. In non-systematic reviews (sometimes called narrative reviews), you don’t have to report the results of all studies and you have more freedom in how you structure your discussion (i.e. tell a narrative). Some non-systematic reviews are excellent and can be extremely useful because they’re generally a bit more reader-friendly. For example, these are a few very good non-systematic reviews (one, two, three, four). However, non-systematic reviews can also be rife with bias and cherry-picking since they’re not conducted in a systematic way, generally meaning systematic reviews provide a more objective and thorough overview of the literature.

Meta-analyses are simply systematic reviews with the addition of statistical analysis. In a meta-analysis, you pool the results of many studies asking the same (or very similar) research questions to get a quantitative overview of the literature. Maybe 10 studies say A is better than B, 5 say there’s no difference, and 2 say B is better than A. Based on the size of those differences, a meta-analysis may show that, when pooling all results together, A is truly significantly better than B, on average. However, if the 5 studies showing no difference were very large trials, or the two studies in favor of B found very large effects, the meta-analysis may find that there’s no significant difference between A and B, on average, in spite of the majority of studies favoring A.

If you’re familiar with the hierarchy of evidence, systematic reviews and meta-analyses are typically considered the highest quality of evidence. That doesn’t mean they’re perfect – if the literature in a given area is of poor quality, you’re left with a garbage-in-garbage-out scenario – but they’re typically considered to be better and more reliable than individual studies.

Image credit: The Logic of Science

Therefore, due to the significance of systematic reviews and meta-analyses, we’ve put together a list and short take-home message of many recent systematic reviews and meta-analyses so you can cut straight to the chase of the results. Many topics related to strength, muscle growth, and nutrition have systematic reviews or meta-analyses covering them. If you’re curious about the research on a given topic, refer back to this list to see if there’s already a systematic review or meta-analysis on the topic. That will give you a better overview than trying to seek out studies one by one (and, if you do want to read the individual studies, it will make your search MUCH easier, since they’ll be referenced in the SR or MA on the topic).

Since there are so many individual systematic reviews or meta-analyses on this list, the overview of each will be really brief. If there are any really major issues, we’ll note them, but for the most part, we’ll just stick to the main findings. Also note that we haven’t included every systematic review or meta-analysis ever done on this list. When there were multiple articles covering the same topic, we went with the one that was more recent or of higher overall quality. If we missed one that you think should be included, let us know in the comments!

To make it easy on you, we split things up by topic. First will be strength, then hypertrophy, then nutrition, then miscellaneous other reviews that are relevant but not neatly categorized.

Just so you’ll know what you’re looking at and reading when viewing the figures below and reading the brief synopses, you’ll need to have an understanding of confidence intervals and forest plots. Confidence intervals (CI) tell you the range of values in which a population average will most likely fall. In meta-analyses, if a confidence interval for comparisons between two different treatments/conditions doesn’t cross zero, then you can state that there’s a statistically significant difference between the two (you have a high level of confidence that the population averages for the two treatments are truly different). Forest plots are figures commonly used in meta-analyses, showing the confidence intervals for multiple studies, along with the pooled average and confidence interval for the entire group of studies.

Here’s an example:

This is a forest plot from a meta-analysis by Schoenfeld et al. looking at the effects of high load vs. low-load training on strength gains. Each black square represents the mean difference in an individual study, while the black bars extending out from that black square represent the confidence interval for that study. The black diamond at the bottom is the confidence interval when pooling the results of all studies. Since the confidence interval doesn’t cross 0, this would be a statistically significant difference, with high-load training leading to significantly larger strength gains than low-load training.

Table of Contents

(Update, March 2021: The rate at which systematic reviews and meta-analyses are being published has picked up considerably in recent years, and demands on my time have also increased substantially from where they were when this page went live in 2018. I’m not sure I’ll be able to keep this page fully updated with summaries and figures for all of the new systematic reviews and meta-analyses moving forward, but I should still have time to provide titles and links for anyone who doesn’t mind doing a tiny bit of legwork. I’ll keep adding the new reviews at the top of each section)

Strength

Training Session and Detraining Duration Affect Lower Limb Muscle Strength Maintenance in Middle-Aged and Older Adults: A Systematic Review and Meta-Analysis. Yang et al. (2021)

Resistance Training with Blood Flow Restriction Compared to Traditional Resistance Training on Strength and Muscle Mass in Non-Active Older Adults: A Systematic Review and Meta-Analysis. Rodrigo-Mallorca et al. (2021)

Resistance Training and Muscle Strength in people with Spinal cord injury: A systematic review and meta-analysis. Santos et al. (2021)

Resistance exercise intervention on muscular strength and power, and functional capacity in acute hospitalized older adults: a systematic review and meta-analysis of 2498 patients in 7 randomized clinical trials. Carneiro et al. (2021)

Machines and free weight exercises: a systematic review and meta-analysis comparing changes in muscle size, strength, and power. Heidel et al. (2021)

Energy deficiency impairs resistance training gains in lean mass but not strength: A meta-analysis and meta-regression. Murphy and Koehler (2021)

Effects of velocity based training vs. traditional 1RM percentage-based training on improving strength, jump, linear sprint and change of direction speed performance: A Systematic review with meta-analysis. Liao et al. (2021)

Effects of Resistance Training Performed with Different Loads in Untrained and Trained Male Adult Individuals on Maximal Strength and Muscle Hypertrophy: A Systematic Review. Lacio et al. (2021)

Effects of resistance training in healthy older people with sarcopenia: a systematic review and meta-analysis of randomized controlled trials. Chen et al. (2021)

Effects of Concurrent Training on 1RM and VO2 in Adults: Systematic Review with Meta-analysis. Pito et al. (2021)

Effects of Circuit Resistance Training on Body Composition, Strength, and Cardiorespiratory Fitness in Middle-Aged and Older Women: A Systematic Review and Meta-Analysis. Ramos-Campos et al. (2021)

Effect of Repetition Duration—Total and in Different Muscle Actions—On the Development of Strength, Power, and Muscle Hypertrophy: A Systematic Review. Moreno-Villanueva et al. (2021)

Does the combination of resistance training and a nutritional intervention have a synergic effect on muscle mass, strength, and physical function in older adults? A systematic review and meta-analysis. Choi et al. (2021)

Contraction fatigue, strength adaptations, and discomfort during conventional versus wide-pulse, high-frequency, neuromuscular electrical stimulation: a systematic review. Bastos et al. (2021)

Compatibility of Concurrent Aerobic and Strength Training for Skeletal Muscle Size and Function: An Updated Systematic Review and Meta-Analysis. Schumann et al. (2021)

Biceps Femoris Activation during Hamstring Strength Exercises: A Systematic Review. Llurda-Almuzara et al. (2021)

Acute and Long-Term Effects of Attentional Focus Strategies on Muscular Strength: A Meta-Analysis. Grgic et al. (2021)

Neuromuscular Electrical Stimulation Training vs. Conventional Strength Training: A Systematic Review and Meta-Analysis of the Effect on Strength Development. Happ and Behringer et al. (2021)

Effects of exercise on muscle mass, strength, and physical performance in older adults with sarcopenia: A systematic review and meta-analysis according to the EWGSOP criteria. Escriche-Escuder et al. (2021)

Effects of range of motion on resistance training adaptations: A systematic review and meta-analysis. Pallarés et al. (2021)

Effects of unilateral vs. bilateral resistance training interventions on measures of strength, jump, linear and change of direction speed: a systematic review and meta-analysis. Liao et al. (2021)

Acute Effects of Wearing Bite-Aligning Mouthguards on Muscular Strength, Power, Agility and Quickness in a Trained Population: A Systematic Review. Miró et al. (2021)

Effects of Velocity-Based Training on Strength and Power in Elite Athletes-A Systematic Review. Włodarczyk et al. (2021)

Moderators of strength gains and hypertrophy in resistance training: A systematic review and meta-analysis. Polito et al. (2021)

Benefits of Resistance Training in Early and Late Stages of Frailty and Sarcopenia: A Systematic Review and Meta-Analysis of Randomized Controlled Studies. Talar et al. (2021)

Teeth clenching can modify the muscle contraction strength of the lower or upper limbs: systematic review. de Souza et al. (2021)

Effects of Resistance Circuit-Based Training on Body Composition, Strength and Cardiorespiratory Fitness: A Systematic Review and Meta-Analysis. Ramos-Campo et al. (2021)

Effects of Variations in Resistance Training Frequency on Strength Development in Well-Trained Populations and Implications for In-Season Athlete Training: A Systematic Review and Meta-analysis. Cuthbert et al. (2021)

Resistance training to reduce resting blood pressure and increase muscle strength in users and non-users of anti-hypertensive medication: A meta-analysis. Polito et al. (2021)

The effects of the Nordic hamstring exercise on sprint performance and eccentric knee flexor strength: A systematic review and meta-analysis of intervention studies among team sport players. Bautista et al. (2021)

Influence of resistance training load on measures of skeletal muscle hypertrophy and improvements in maximal strength and neuromuscular task performance: A systematic review and meta-analysis. Refalo et al. (2021)

Effects of resistance training interventions on muscular strength in adults with intellectual disability: a systematic review and meta-analysis. Obrusnikova et al. (2021)

Development of Maximal Dynamic Strength During Concurrent Resistance and Endurance Training in Untrained, Moderately Trained, and Trained Individuals: A Systematic Review and Meta-analysis. Petré et al. (2021)

Effects of Resistance Training Performed to Failure or Not to Failure on Muscle Strength, Hypertrophy, and Power Output: A Systematic Review With Meta-Analysis. Vieira et al. (2021)

Auto-Regulation Method vs. Fixed-Loading Method in Maximum Strength Training for Athletes: A Systematic Review and Meta-Analysis. Zhang et al. (2021)

Resistance Training Load Effects on Muscle Hypertrophy and Strength Gain. Lopez et al. (2020)

This meta is an updated and expanded meta looking at the same question the Schoenfeld (2017) meta examined: the impact of intensity on strength gains. This meta split loading zones into “high load” (8RM or heavier), “moderate load” (9-15RM), and “low load” (lighter than 15RM). It found that moderate- and high-load training led to larger strength gains than low-load training, but that high-load training didn’t lead to significantly larger strength gains than moderate-load training. However, it’s worth noting that the difference between moderate- and high-load training was nearly significant (p<0.07) in favor of high loads. I suspect that high load training is actually superior, but the meta-analysis lacked statistical power. It’s also worth noting that most of the subjects in the included studies were untrained; I suspect that the difference between moderate-load and high-load training is larger for more experienced lifters.

lopez strength


Effects of subjective and objective autoregulation methods for intensity and volume on enhancing maximal strength during resistance-training interventions: a systematic review. Larsen et al. (2021)

This was just a really solid review of the extant studies investigating various autoregulation methods, but there’s no meta-analytic component comparing autoregulation against inflexible training prescriptions. The basic conclusion is that autoregulation can work when programming for strength development. I’d primarily recommend this paper as a good resource for acquainting yourself with this body of literature.


Chronic Effects of Altering Resistance Training Set Configurations Using Cluster Sets: A Systematic Review and Meta-Analysis. Davies et al. (2021)

Cluster sets and traditional sets seem to produce similar strength gains. Another recent meta-analysis by Jukic and colleagues comparing traditional sets with both cluster sets and rest redistribution sets had similar findings. However, cluster sets and rest redistribution sets may be superior for improving velocities with submaximal loads, while traditional sets may be superior for improving strength endurance.

Davies cluster sets strength


The Effects of Regular Cold-Water Immersion Use on Training-Induced Changes in Strength and Endurance Performance: A Systematic Review with Meta-Analysis. Malta et al. (2020)

Cold-water immersion after workouts seems to have a negative impact on training-induced improvements in strength (assessed via 1RM strength, maximal isometric strength, strength endurance, and ballistic strength). However, aerobic adaptations seem to be unaffected.


Classic Powerlifting Performance: A Systematic Review. Ferland and Comtois (2019)

It would be hard to summarize this article without basically just copying and pasting the abstract. More than anything, it would be a good article to mine for references if you want to see the state of the research on raw powerlifters across a wide array of outcomes.


Effect of blood‐flow restricted vs heavy‐load strength training on muscle strength: Systematic review and meta‐analysis. Grønfeldt et al. (2020)

Low-load training (20-50% 1RM) with blood flow restriction produces strength gains that are not significantly different from strength training without blood flow restriction in more traditional intensity ranges (60-90% 1RM). However, the mean effect leans in favor of heavier training without BFR, and the difference would likely be larger in well-trained populations. However, if gaining strength is a primary training goal, and you choose to do low-load training for some reason, using BFR for your low-load training may not be a bad idea. A slightly older meta-analysis did find a significant difference in strength gains in favor of heavier traditional training; it also found that low-load training the BFR and heavier traditional training led to similar muscle growth.


Effects of Dynamic Resistance Exercise on Bone Mineral Density in Postmenopausal Women: A Systematic Review and Meta-Analysis With Special Emphasis on Exercise Parameters. Shojaa et al. (2020)

In postmenopausal women, resistance exercise is effective for increasing or better-preserving bone mineral density of the lumbar spine, femoral neck, and total hip. Another meta by the same group had similar findings. Furthermore, training intensity may not have much of an impact on the benefits of resistance training for bone mineral density, but more research is needed on the topic.


Resistance training induced changes in strength and specific force at the fiber and whole muscle level: a meta-analysis. Dankel et al (2018)

Strength gains on a whole-muscle level generally exceed strength gains on a fiber level following resistance training. Furthermore, following resistance training, type I fiber specific tension generally increases, while type II fiber specific tension does not increase to a statistically significant degree.


Sex Differences in Resistance Training: A Systematic Review and Meta-Analysis. Roberts et al (2020).

Relative (e.g. percentage) increases in muscle mass and lower body strength following resistance training are similar between the sexes. Relative increases in upper body strength tend to be larger in females. This is a more formalized version of a meta-analysis that previously appeared on Stronger By Science. A more recent meta on older adults (>50 years old) had broadly similar findings: on a relative basis, lower body strength gains were larger in females, while hypertrophy and upper body strength gains were similar between sexes; conversely, absolute hypertrophy and strength gains were larger in males.


The Minimum Effective Training Dose Required to Increase 1RM Strength in Resistance-Trained Men: A Systematic Review and Meta-Analysis. Androulakis-Korakakis et al. (2020)

One set taken to failure or very close to failure, 2-3x per lift per week, with ~70-85% 1RM is sufficient for intermediate-level lifters to still make strength gains in the squat and bench press.


Variations in strength-related measures during the menstrual cycle in eumenorrheic women: A systematic review and meta-analysis. Blagrove et al. (2020)

Strength does not seem to fluctuate significantly throughout the menstrual cycle in eumenorrheic females. This study was previously reviewed in more detail in MASS.


The Effects of Menstrual Cycle Phase on Exercise Performance in Eumenorrheic Women: A Systematic Review and Meta-Analysis. McNulty et al. (2020)

Exercise performance may be slightly reduced in the early follicular phase of the menstrual cycle (e.g. during menstruation). However, the average magnitude of the effect is trivial (d = 0.01-0.14), and the only statistically significant difference is between the early and late follicular phases.


What influence does resistance exercise order have on muscular strength gains and muscle hypertrophy? A systematic review and meta-analysis. Nunes et al. (2020)

Exercise order (multi-joint exercises before single-joint, versus single-joint exercises before multi-joint) significantly affects strength gains; you generally gain more strength in the exercises you train earlier in a training session. However, exercise order does not seem to significantly impact muscle growth. This study was previously discussed in more depth in MASS.


Systematic review and meta-analysis of linear and undulating periodized resistance training programs on muscular strength. Harries et al. (2015)

Linear and undulating periodization approaches led to similar increases in bench press and squat strength. While there was no significant difference, results tended to favor undulating periodization for leg press strength (p=0.07).


The Effect of Weekly Set Volume on Strength Gain: A Meta-Analysis. Ralston et al. (2017)

Higher weekly set volume (5-10+) led to larger strength gains than lower week set volumes (<5). This held true for both compound and single-joint exercises. The differences weren’t quite as large as many people might expect (i.e. substantially higher volume for ~20% faster gains), but they were statistically significant and definitely meaningful for people trying to maximize strength. However, substantial strength gains were also possible with low weekly set volume. These findings mirror those of an earlier meta-analysis by Kreiger: Single versus multiple sets of resistance exercise: a meta-regression. This meta-analysis was discussed in more detail in Volume 1, Issue 6 of MASS.


Comparison of Periodized and Non-Periodized Resistance Training on Maximal Strength: A Meta-Analysis. Williams et al. (2017)

Periodized training led to significantly larger strength gains than non-periodized training. The difference was considered a small effect. However, there was some evidence of publication bias, with several studies showing outsized results in favor of periodized training beyond what would be expected without bias. When they were removed, the mean effect in favor of periodized training was roughly halved, but it was still significant. This should sound familiar to Stronger By Science readers. This meta-analysis was also discussed in more depth in Volume 1, Issue 4 of MASS.


Concurrent training: a meta-analysis examining interference of aerobic and resistance exercises. Wilson et al. (2012)

Concurrent training (doing both strength and endurance training) led to smaller lower body strength and power gains than strength training alone. There were no differences for upper body strength gains. The difference for lower body strength gains depended on the cardio modality used, though. There was a significant difference between concurrent training and strength training alone when running was the cardio modality, but not when cycling was used instead (however, when looking at the raw effect sizes, it does seem that cycling still had some negative impacts, that just weren’t large enough to reach significance). There were no differences for upper body strength gains. Moderating factors included frequency and duration, such that more frequent cardio and longer duration cardio tended to decrease lower body strength and power gains to a greater degree than less frequent or shorter duration cardio.


The compatibility of concurrent high intensity interval training and resistance training for muscular strength and hypertrophy: a systematic review and meta-analysis. Sabag et al. (2018)

Much like the Wilson meta-analysis (which primarily used studies employing low-intensity cardio) on the interference effect with concurrent training, this meta-analysis found that combining resistance training and HIIT led to smaller gains in lower body strength than resistance training alone, while upper body strength gains were unaffected. Unlike the Wilson meta-analysis, cycle sprints seemed to negatively affect strength gains more than running sprints (though the difference between modalities wasn’t significant). No interference effect on strength gains was observed in studies allowing at least 24 hours of rest between lifting and HIIT sessions.


The Role of Intra-Session Exercise Sequence in the Interference Effect: A Systematic Review with Meta-Analysis. Eddens et al. (2018)

If you need to do strength training and aerobic training within the same session, this meta-analysis found that session order (i.e. lifting first or cardio first) didn’t affect gains in aerobic fitness, changes in body fat percentage, or lower body isometric strength, but it did affect lower body dynamic strength. Lifting first in the session, followed by cardio, led to larger strength gains than doing cardio first. The difference wasn’t particularly large (~7% larger strength gains), but it was significant. A 2017 meta-analysis on the same topic by Murlasits et al. came to similar conclusions, but only looked at dynamic strength and aerobic fitness.

Dynamic strength, from Eddens et al. (2018)

Strength and Hypertrophy Adaptations Between Low- vs. High-Load Resistance Training: A Systematic Review and Meta-analysis. Schoenfeld et al. (2017)

This meta-analysis found that, unsurprisingly, heavy training (>60% of 1RM) led to larger gains in dynamic strength than low-load training (≤60% of 1RM). However, there was no significant difference for isometric strength. This meta-analysis was also discussed in more depth in Volume 1, Issue 7 of MASS.

Dynamic strength, from Shoenfeld et al. (2017)

Effect of Resistance Training Frequency on Gains in Muscular Strength: A Systematic Review and Meta-Analysis. Grgic et al. (2018)

This meta-analysis found that higher training frequencies are associated with larger strength gains. However, in studies where volume was equated despite different frequencies (weekly volume was higher in the higher frequency groups in many studies), higher frequencies weren’t associated with larger strength gains. This meta-analysis was discussed in Volume 2, Issue 4 of MASS, along with an additional analysis of just the studies using trained lifters.


Effect of Movement Velocity During Resistance Training on Dynamic Muscular Strength: A Systematic Review and Meta-Analysis. Davies et al. (2017)

This meta-analysis found that, when controlling for intensity and volume, lifting velocity didn’t significantly affect strength gains. However, it should be noted that several of the studies in this meta-analysis involved training to failure, meaning the velocity differences may have only existed for the first few reps. It also included a few studies using protocols where the training would have been very easy for both groups (i.e. 3×8 at 50% of 1RM) where you wouldn’t expect big strength gains in either group.


Effect of Training Leading to Repetition Failure on Muscular Strength: A Systematic Review and Meta-Analysis. Davies et al. (2016); also check the erratum

This meta-analysis found that training to failure vs. stopping short of failure didn’t significantly affect strength gains. That was true both for studies where volume was controlled, and for studies where volume wasn’t controlled.


Effects of Variable Resistance Training on Maximal Strength: A Meta-Analysis. Soria-Gila et al (2015)

This meta-analysis was retracted after a re-analysis found several errors in the original publication. When those errors were corrected, there was effectively no difference between training with straight weight vs. including bands and chains.


Is inertial flywheel resistance training superior to gravity-dependent resistance training in improving muscle strength? A systematic review with meta-analyses. Vicens-Bordas et al. (2018)

This meta-analysis found that flywheel training devices led to similar strength gains compared to gravity-dependent resistance training (i.e. free weights, or most of the machines you’d find a typical gym). This was honestly probably an area of research that wasn’t quite ready for a meta-analysis (only seven studies). 


Effects of weightlifting exercise, traditional resistance and plyometric training on countermovement jump performance: a meta-analysis. Berton et al. (2018)

Weightlifting exercises (the clean & jerk, the snatch, and their derivatives) seem to increase countermovement jump performance to a greater degree than traditional resistance exercises. Weightlifting exercises and plyometrics seem to be equally effective at increasing countermovement jump performance.


The efficacy of resistance training in hypoxia to enhance strength and muscle growth: A systematic review and meta-analysis. Ramos-Campo et al (2018)

This meta-analysis found that strength gains after training in hypoxia (i.e. conditions that simulate being at high altitudes using environmental chambers, not using something like “altitude training masks”) were similar in magnitude to strength gains after training with normal oxygen availability. There aren’t many studies on this topic yet, so this meta-analysis may have been a bit premature.


Effects and Dose-Response Relationships of Motor Imagery Practice on Strength Development in Healthy Adult Populations: a Systematic Review and Meta-analysis. Paravlic et al. (2018)

This meta-analysis found that motor imagery training led to significant strength gains compared to no training, but that a combination of motor imagery and physical training didn’t lead to larger strength gains than physical training alone. However, it’s worth noting that a recent study not included in this meta-analysis (since it was published after they’d completed their literature search) did find that a combination of motor imagery and physical training led to larger strength gains than physical training alone. However, that’s still just the fifth study testing a combination of physical training and motor imagery vs. physical training alone, so that’s an area badly in need of more research. As it is, it seems that the main application of motor imagery training would be to aid in maintaining performance when you need to take time off training for some reason (injury, vacation, etc.).


Dose–Response Relationships of Resistance Training in Healthy Old Adults: A Systematic Review and Meta-Analysis. Borde et al. (2015)

Older people can get stronger and jacked-er too! This meta-analysis was simply intended to determine the training variables associated with the largest increases in strength and muscle size in older adults. I think the most important finding was that the training doses that work best in older adults look really similar to what tends to work best in younger adults as well, except with slightly lower volume and intensity.


Effects and dose–response relationships of resistance training on physical performance in youth athletes: a systematic review and meta-analysis. Lesinski et al. (2016)

Similar to the meta-analysis on older adults, this meta-analysis was simply intended to determine the training variables associated with the largest increases in performance in young athletes. Again, their findings largely mirror what are usually considered good general training practices: long-term training (>23 weeks), with a frequency of 1-3x per exercise per week, high-ish intensities (80-89% of 1RM), high volumes (5 sets per exercise beat out 1-4 sets per exercise), a moderate number of reps per set (6-8), and long rest duration (3-4 minutes between sets) was found to promote the largest strength gains.

A more recent umbrella review, also by Lesinski and colleagues, delves even deeper into the topic of resistance training for youth and adolescent athletes. It gives an overview of all of the systematic reviews and meta-analyses ever performed related to the effects of resistance training in children and adolescents. It’s worth checking out if you train young lifters.


A Meta-Analysis of Resistance Training in Female Youth: Its Effect on Muscular Strength, and Shortcomings in the Literature. Moran et al. (2018)

Strength training is effective for increasing strength in young females. However, the effect is about twice as large for older adolescents (>15 years old) than younger adolescents (15 years old or younger).


Supramaximal Eccentrics Versus Traditional Loading in Improving Lower-Body 1RM: A Meta-Analysis. Buskard et al. (2018)

Supramaximal eccentric training involves lowering heavier weights than you can lift concentrically. This meta-analysis found that supramaximal eccentric training didn’t lead to larger 1RM increases than traditional training (i.e. with submaximal eccentrics and concentrics). However, the only study that used a free weight compound exercise (squats) did find a benefit for supramaximal eccentric training. So, while it doesn’t seem that supramaximal eccentrics aid in 1RM strength development in single-joint or machine exercises, it’s probably prudent to wait for most studies using compound free weight exercises before coming to a strong conclusion regarding their efficacy for powerlifting.


Muscle growth

The Effect of Resistance Training on Body Composition During and After Cancer Treatment: A Systematic Review and Meta-Analysis. Clifford et al. (2021)

Resistance Training with Blood Flow Restriction Compared to Traditional Resistance Training on Strength and Muscle Mass in Non-Active Older Adults: A Systematic Review and Meta-Analysis. Rodrigo-Mallorca et al. (2021)

Machines and free weight exercises: a systematic review and meta-analysis comparing changes in muscle size, strength, and power. Heidel et al. (2021)

Energy deficiency impairs resistance training gains in lean mass but not strength: A meta-analysis and meta-regression. Murphy and Koehler. (2021)

Effects of Resistance Training Performed with Different Loads in Untrained and Trained Male Adult Individuals on Maximal Strength and Muscle Hypertrophy: A Systematic Review. Lacio et al. (2021)

Effects of resistance training in healthy older people with sarcopenia: a systematic review and meta-analysis of randomized controlled trials. Chen et al. (2021)

Effects of Circuit Resistance Training on Body Composition, Strength, and Cardiorespiratory Fitness in Middle-Aged and Older Women: A Systematic Review and Meta-Analysis. Ramos-Campo et al. (2021)

Effect of Repetition Duration—Total and in Different Muscle Actions—On the Development of Strength, Power, and Muscle Hypertrophy: A Systematic Review. Moreno-Villanueva et al. (2021)

Does the combination of resistance training and a nutritional intervention have a synergic effect on muscle mass, strength, and physical function in older adults? A systematic review and meta-analysis. Choi et al. (2021)

Compatibility of Concurrent Aerobic and Strength Training for Skeletal Muscle Size and Function: An Updated Systematic Review and Meta-Analysis. Schumann et al. (2021)

Effects of exercise on muscle mass, strength, and physical performance in older adults with sarcopenia: A systematic review and meta-analysis according to the EWGSOP criteria. Escriche-Escuder et al. (2021)

Effects of range of motion on resistance training adaptations: A systematic review and meta-analysis. Pallarés et al. (2021)

Moderators of strength gains and hypertrophy in resistance training: A systematic review and meta-analysis. Polito et al. (2021)

Benefits of Resistance Training in Early and Late Stages of Frailty and Sarcopenia: A Systematic Review and Meta-Analysis of Randomized Controlled Studies. Talar et al. (2021)

Protein Source and Quality for Skeletal Muscle Anabolism in Young and Older Adults: A Systematic Review and Meta-Analysis. Morgan et al. (2021)

Influence of resistance training load on measures of skeletal muscle hypertrophy and improvements in maximal strength and neuromuscular task performance: A systematic review and meta-analysis. Refalo et al. (2021)

The effect of resistance training programs on lean body mass in postmenopausal and elderly women: a meta-analysis of observational studies. Thomas et al. (2021)

Effects of Resistance Training Performed to Failure or Not to Failure on Muscle Strength, Hypertrophy, and Power Output: A Systematic Review With Meta-Analysis. Vieira et al. (2021)

Resistance Training Load Effects on Muscle Hypertrophy and Strength Gain. Lopez et al. (2020)

This meta is an updated and expanded meta looking at the same question the Schoenfeld (2017) meta examined: the impact of intensity on muscle growth. This meta split loading zones into “high load” (8RM or heavier), “moderate load” (9-15RM), and “low load” (lighter than 15RM). It found that hypertrophy was similar in all three loading zones.

lopez hypertrophy


Chronic Effects of Altering Resistance Training Set Configurations Using Cluster Sets: A Systematic Review and Meta-Analysis. Davies et al. (2021)

Cluster sets and traditional sets seem to produce similar hypertrophy. Another recent meta-analysis by Jukic and colleagues comparing traditional sets with both cluster sets and rest redistribution sets had similar findings.

davies cluster sets hypertrophy


Regional Hypertrophy, the Inhomogeneous Muscle Growth: A Systematic Review. Zabaleta-Korta et al. (2020).

Regional hypertrophy (greater growth in some regions of a muscle compared to other regions) can occur, and seems to be the rule, rather than the exception. Of the 14 studies included in this review, inhomogenous hypertrophy was observed in 13 of them.


Effects of range of motion on muscle development during resistance training interventions: A systematic review. Schoenfeld and Grgic. (2020)

We have fairly consistent evidence indicating that training through a longer range of motion is beneficial for lower body hypertrophy (quad growth, specifically). There haven’t been many studies investigating upper body hypertrophy yet. This study was previously discussed in more depth in MASS.


Gluteus Maximus Activation during Common Strength and Hypertrophy Exercises: A Systematic Review. Neto et al. (2020)

Step-up, hip thrust, and deadlift variations do a pretty good job of eliciting high levels of glute EMG activity. Lunges and squat variations are also pretty good.


Isometric training and long‐term adaptations: Effects of muscle length, intensity, and intent: A systematic review. Oranchuk et al. (2018)

“Isometric training at longer muscle lengths produced greater muscular hypertrophy when compared to equal volumes of shorter muscle length training. Ballistic intent resulted in greater neuromuscular activation and rapid force production. Substantial improvements in muscular hypertrophy and maximal force production were reported regardless of training intensity. High‐intensity (≥70%) contractions are required for improving tendon structure and function. Additionally, long muscle length training results in greater transference to dynamic performance.”


Maximizing Muscle Hypertrophy: A Systematic Review of Advanced Resistance Training Techniques and Methods. Krzysztofik et al. (2019)

It’s not even worth attempting to summarize this systematic review, but if you’re interested in seeing what literature is out there regarding “advanced techniques” in resistance training (drop sets, rest-paused sets, etc.), you should check out this article to find all of the relevant studies in one place.


Muscle Fiber Hypertrophy and Myonuclei Addition: A Systematic Review and Meta-analysis. Conceiçäo et al. (2018)

“Muscle fiber hypertrophy of ≤10% induces increases in myonuclear content, although a significantly higher number of myonuclei are observed when muscle hypertrophy is ~22%. Additional analyses showed that age, sex, and muscle fiber type do not influence muscle fiber hypertrophy or myonuclei addition.”


Effects of linear and daily undulating periodized resistance training programs on measures of muscle hypertrophy: a systematic review and meta-analysis. Grgic et al. (2017)

This meta-analysis found that both linear and daily undulating periodized training had similar effects on muscle growth. This meta-analysis was discussed in more depth in Volume 1, Issue 7 of MASS.


Should resistance training programs aimed at muscular hypertrophy be periodized? A systematic review of periodized versus non-periodized approaches Grgic et al. (2017)

This systematic review found that, at least in the short term (i.e. a few months), periodized and non-periodized training have similar effects on muscle growth.


Dose-response relationship between weekly resistance training volume and increases in muscle mass: A systematic review and meta-analysis. Schoenfeld et al. (2017)

This meta-analysis found that higher training volumes were associated with more muscle growth. There was an essentially linear relationship, with <5 sets per week leading to a 5.4% increase in muscle size, 5-9 sets per week leading to a 6.6% increase in muscle size, and 10+ sets per week leading to 9.8% increase in muscle size. However, there was one outlier that strongly influenced the results. When it was removed, the overall trend still held, but the overall effect shrunk. Before removal, each additional set was worth an additional 0.37% increase, on average; after its removal, each additional set was worth an additional 0.25% increase, on average. These results are very similar to those of an earlier meta-analysis by Kreiger: Single vs. multiple sets of resistance exercise for muscle hypertrophy: a meta-analysis.


Hypertrophic Effects of Concentric vs. Eccentric Muscle Actions: A Systematic Review and Meta-analysis. Schoenfeld et al. (2017)

This meta-analysis found no significant differences between concentric and eccentric training for hypertrophy. However, results tended to favor eccentric training (10% vs. 6.8%; p=0.076). However, since most exercises have both an eccentric and concentric component, this probably isn’t a big deal since you’ll be performing both muscle actions in most of your training. For more on eccentric training, this systematic review by Douglas et al. is also well worth a read.


Concurrent training: a meta-analysis examining interference of aerobic and resistance exercises. Wilson et al. (2012)

As with the strength findings from this same meta-analysis (presented earlier in this article), concurrent training led to less lower body hypertrophy than strength training alone. However, this difference was also mediated by aerobic training modality; there was a significant difference when running was the aerobic modality, but not when cycling was the aerobic modality (though nominal effect sizes still tended to favor strength training alone).


The compatibility of concurrent high intensity interval training and resistance training for muscular strength and hypertrophy: a systematic review and meta-analysis. Sabag et al. (2018)

Unlike the Wilson meta-analysis (which primarily used studies employing low-intensity cardio) on the interference effect with concurrent training, this meta-analysis found that combining resistance training and HIIT led to just as much hypertrophy as resistance training alone.


The Role of Intra-Session Exercise Sequence in the Interference Effect: A Systematic Review with Meta-Analysis. Eddens et al. (2018)

Unlike the strength findings from this same meta-analysis, session order didn’t have a significant effect on hypertrophy. If you have to do strength training and cardio in the same session, the order you do them in probably won’t have much of an effect on lower body muscle growth.


Effect of repetition duration during resistance training on muscle hypertrophy: a systematic review and meta-analysis. Schoenfeld et al. (2015)

This meta-analysis found that repetition duration didn’t significantly affect hypertrophy. As long as you’re training hard, whether you like lifting explosively or purposefully slowing your reps down, muscle growth will probably be similar. It’s worth noting that there weren’t enough studies with really long rep durations (10+ seconds) to meta-analyze, but preliminary results indicate that with super slow reps, hypertrophy may be diminished to some degree.


Strength and Hypertrophy Adaptations Between Low- vs. High-Load Resistance Training: A Systematic Review and Meta-analysis. Schoenfeld et al (2017)

Unlike the dynamic strength findings from this same meta-analysis, hypertrophy was unaffected by training intensity. Both high load (>60% of 1RM) and low load (≤60% of 1RM) training caused similar muscle growth. It’s worth noting that all of these studies had people train to failure. This conclusion should sound familiar to Stronger By Science readers. A more recent meta-analysis examining the effects of high and low load training on muscle fiber hypertrophy also observed similar hypertrophy in both general loading zones.


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. Schoenfeld et al. (2018)

When volume is equated, training frequency doesn’t seem to have much of an impact on muscle growth. When volume isn’t equated (i.e. when higher frequencies mean higher volumes), higher frequencies generally yield more muscle growth.


Effect of movement velocity during resistance training on muscle-specific hypertrophy: A systematic review. Hackett et al. (2018)

This was a systematic review found that moderate-to-slow velocities (2-3 second eccentrics and concentrics) may lead to more quad growth than faster velocities (~1 second eccentrics and concentrics), while faster velocities may lead to more biceps growth. Specifically, three of five studies found greater quad hypertrophy with slower rep velocities (two found no difference), while two studies found greater biceps hypertrophy with faster rep velocities. However, this systematic review covered just six studies, so the findings are very tentative.


The efficacy of resistance training in hypoxia to enhance strength and muscle growth: A systematic review and meta-analysis. Ramos-Campo et al. (2018)

Similar to the strength findings from this same meta-analysis (presented earlier in this article), hypertrophy was similar when training under both hypoxic and normoxic conditions. Again, there weren’t many studies included in this meta-analysis, so results are very tentative.


The effects of short versus long inter-set rest intervals in resistance training on measures of muscle hypertrophy: A systematic review. Grgic et al. (2017)

There were six studies included in this analysis comparing short (20-60 seconds) and long (>60 seconds) rest intervals. Hypertrophy tended to be greater with longer rest intervals (9.2% vs. 5.8%), but there was considerable heterogeneity. Ultimately, the authors simply conclude that robust hypertrophy can occur with both short and longer rest intervals, but that more research is needed.


Dose–Response Relationships of Resistance Training in Healthy Old Adults: A Systematic Review and Meta-Analysis. Borde et al. (2015)

The table for hypertrophy recommendations was previously presented. Again, just notice how the recommendations for older adults largely mirror those for younger adults, except that recommended volume and intensity is a bit lower.


Nutrition and Supplementation

The use of BCAA to decrease delayed-onset muscle soreness after a single bout of exercise: a systematic review and meta-analysis. Weber et al. (2021)

The Hydrating Effects of Hypertonic, Isotonic and Hypotonic Sports Drinks and Waters on Central Hydration During Continuous Exercise: A Systematic Meta-Analysis and Perspective. Rowlands et al. (2021)

The effects of collagen peptide supplementation on body composition, collagen synthesis, and recovery from joint injury and exercise: a systematic review. Khatri et al. (2021)

The effect of branched-chain amino acid on muscle damage markers and performance following strenuous exercise: a systematic review and meta-analysis. Doma et al. (2021)

Protein interventions augment the effect of resistance exercise on appendicular lean mass and handgrip strength in older adults: a systematic review and meta-analysis of randomized controlled trials. Kirwan et al. (2021)

Pre-Exercise Whole- or Partial-Body Cryotherapy Exposure to Improve Physical Performance: A Systematic Review. Partridge et al. (2021)

Post-exercise energy intake: do the intensity and mode of exercise matter? A systematic review and meta-analysis comparing high-intensity interval with moderate-intensity continuous protocols. Rossi et al. (2021)

Low-calorie sweeteners and human health: a rapid review of systematic reviews. Andrade et al. (2020)

Extracellular Buffering Supplements to Improve Exercise Capacity and Performance: A Comprehensive Systematic Review and Meta-analysis. de Oliveira et al. (2021)

Examining the effects of calorie restriction on testosterone concentrations in men: a systematic review and meta-analysis. Smith et al. (2021)

Energy deficiency impairs resistance training gains in lean mass but not strength: A meta-analysis and meta-regression. Murphy and Koehler. (2021)

Efficacy of Creatine Supplementation Combined with Resistance Training on Muscle Strength and Muscle Mass in Older Females: A Systematic Review and Meta-Analysis. dos Santos et al. (2021)

Effects of Vitamin D in Post-Exercise Muscle Recovery. A Systematic Review and Meta-Analysis. Bello et al. (2021)

Effect of Time-Restricted Feeding on Anthropometric, Metabolic, and Fitness Parameters: A Systematic Review. Kang et al. (2021)

Effect of Polyphenol-Rich Foods, Juices, and Concentrates on Recovery from Exercise Induced Muscle Damage: A Systematic Review and Meta-Analysis. Rickards et al. (2021)

Effect of dietary nitrate on human muscle power: a systematic review and individual participant data meta-analysis. Coggan et al. (2021)

Does the combination of resistance training and a nutritional intervention have a synergic effect on muscle mass, strength, and physical function in older adults? A systematic review and meta-analysis. Choi et al. (2021)

Does Acute Caffeine Supplementation Improve Physical Performance in Female Team-Sport Athletes? Evidence from a Systematic Review and Meta-Analysis. Gomez-Bruton et al. (2021)

Clinical Effects of L-Carnitine Supplementation on Physical Performance in Healthy Subjects, the Key to Success in Rehabilitation: A Systematic Review and Meta-Analysis from the Rehabilitation Point of View. Vecchio et al. (2021)

Caffeinated Drinks and Physical Performance in Sport: A Systematic Review. Jiménez et al. (2021)

Effect of Carnosine or β-Alanine Supplementation on Markers of Glycemic Control and Insulin Resistance in Humans and Animals: A Systematic Review and Meta-analysis. Matthews et al. (2021)

Effects of Milk Protein in Resistance Training-Induced Lean Mass Gains for Older Adults Aged ≥ 60 y: A Systematic Review and Meta-Analysis. Huang et al. (2021)

The association between food insecurity and dietary outcomes in university students: a systematic review. Shi et al. (2021)

The Dose Response of Taurine on Aerobic and Strength Exercises: A Systematic Review. Chen et al. (2021)

The Effect of Meal Replacement on Weight Loss According to Calorie-Restriction Type and Proportion of Energy Intake: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Min et al. (2021)

Meta-Analysis Examining the Importance of Creatine Ingestion Strategies on Lean Tissue Mass and Strength in Older Adults. Forbes et al. (2021)

The effects of low-fat, high-carbohydrate diets vs. low-carbohydrate, high-fat diets on weight, blood pressure, serum liquids and blood glucose: a systematic review and meta-analysis. Yang et al. (2021)

Omega-3 long-chain polyunsaturated fatty acid and sleep: a systematic review and meta-analysis of randomized controlled trials and longitudinal studies. Dai and Liu (2021)

Effects of Citrulline Malate Supplementation on Muscle Strength in Resistance-Trained Adults: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Aguiar et al. (2021)

Ergogenic Effects of Acute Caffeine Intake on Muscular Endurance and Muscular Strength in Women: A Meta-Analysis. Grgic and Del Coso. (2021)

Body composition changes in physically active individuals consuming ketogenic diets: a systematic review. Coleman et al. (2021)

Green Tea and Black Tea for Exercise Recovery: A Systematic Review. Zapata and Hewlings. (2021)

N-3 PUFA as an ergogenic supplement modulating muscle hypertrophy and strength: a systematic review. López-Seoane et al. (2021)

Pre-Sleep Casein Supplementation, Metabolism, and Appetite: A Systematic Review. Dela Cruz and Kahan. (2021)

The Effect of Nitrate-Rich Beetroot Juice on Markers of Exercise-Induced Muscle Damage: A Systematic Review and Meta-Analysis of Human Intervention Trials. Jones et al. (2021)

The Impact of Vegan Diet in the Prevention and Treatment of Type 2 Diabetes: A Systematic Review. Pollakova et al. (2021)

Does Branched-Chain Amino Acids (BCAAs) Supplementation Attenuate Muscle Damage Markers and Soreness after Resistance Exercise in Trained Males? A Meta-Analysis of Randomized Controlled Trials. Khemtong et al. (2021)

Effect of Probiotic Consumption on Immune Response in Athletes: A Meta-analysis. Tavakoly et al. (2021)

The Effect of Sodium Bicarbonate Supplementation on Electromyographic Muscle Activity in Healthy, Physically Active Individuals: A Systematic Review. Kalytczak et al. (2021)

The impact of tryptophan supplementation on sleep quality: a systematic review, meta-analysis, and meta-regression. Sutanto et al. (2021)

Low-fat diets and testosterone in men: Systematic review and meta-analysis of intervention studies. Whittaker and Wu (2021)

Effects of nonnutritive sweeteners on body weight and BMI in diverse clinical contexts: Systematic review and meta-analysis. Laviada-Molina et al. (2020)

Effects of intermittent fasting combined with resistance training on body composition: a systematic review and meta-analysis. Ashtary-Larky et al. (2021)

Does Protein Supplementation Support Adaptations to Arduous Concurrent Exercise Training? A Systematic Review and Meta-Analysis with Military Based Applications. Chapman et al. (2021)

Acute Effect of Citrulline Malate on Repetition Performance During Strength Training: A Systematic Review and Meta-Analysis. Vårvik et al. (2021)

A Systematic Review, Meta-Analysis and Meta-Regression on the Effects of Carbohydrates on Sleep. Vlahoyiannis et al. (2021)

The effect of leaf extract supplementation on exercise-induced muscle damage and muscular performance: A systematic review and meta-analysis. Doma et al. (2021)

The Effect of Creatine Supplementation on Markers of Exercise-Induced Muscle Damage: A Systematic Review and Meta-Analysis of Human Intervention Trials. Northeast and Clifford (2021)

Protein Source and Quality for Skeletal Muscle Anabolism in Young and Older Adults: A Systematic Review and Meta-Analysis. Morgan et al. (2021)

A Systematic Review of the Association Between Vegan Diets and Risk of Cardiovascular Disease. Kaiser et al. (2021)

Do Lower-Carbohydrate Diets Increase Total Energy Expenditure? An Updated and Reanalyzed Meta-Analysis of 29 Controlled-Feeding Studies. Ludwig et al. (2021)

The Influence of Mindful Eating and/or Intuitive Eating Approaches on Dietary Intake: A Systematic Review. Grider et al. (2021)

Tart Cherry Supplementation and Recovery From Strenuous Exercise: A Systematic Review and Meta-Analysis. Hill et al. (2021)

Flavonoid Containing Polyphenol Consumption and Recovery from Exercise-Induced Muscle Damage: A Systematic Review and Meta-Analysis. Carey et al. (2021)

Effects of Isolated and Combined Ingestion of Sodium Bicarbonate and β-Alanine on Combat Sports Athletes’ Performance: A Systematic Review. Lopes-Silva et al. (2021)

The effect of magnesium supplementation on anthropometric indices: a systematic review and dose–response meta-analysis of clinical trials. Rafiee et al. (2020)

Sodium bicarbonate supplementation and the female athlete: A brief commentary with small scale systematic review and meta-analysis. Saunders et al. (2021)

Is Probiotic Supplementation Useful for the Management of Body Weight and Other Anthropometric Measures in Adults Affected by Overweight and Obesity with Metabolic Related Diseases? A Systematic Review and Meta-Analysis. Perna et al. (2021)

Factors influencing the efficacy of nutritional interventions on muscle mass in older adults: a systematic review and meta-analysis. Martin-Cantero et al. (2021)

Efficacy of Alternative Forms of Creatine Supplementation on Improving Performance and Body Composition in Healthy Subjects: A Systematic Review. Fazio et al. (2021)

Effects of pre-sleep protein consumption on muscle-related outcomes — A systematic review. Reis et al. (2021)

Effects of Ashwagandha (Withania somnifera) on Physical Performance: Systematic Review and Bayesian Meta-Analysis. Bonilla et al. (2021)

Effect of dietary nitrate ingestion on muscular performance: a systematic review and meta-analysis of randomized controlled trials. Alvares et al. (2021)

Animal Protein versus Plant Protein in Supporting Lean Mass and Muscle Strength: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Lim et al. (2021)

A Systematic Review and Meta-analysis of the Effect of Multi-ingredient Preworkout Supplementation on Strength, Exercise Volume, and Anaerobic Capacity in Healthy Resistance-Trained Individuals. Bobos et al. (2021)

Capsaicinoid and Capsinoids as an Ergogenic Aid: A Systematic Review and the Potential Mechanisms Involved. Vilton et al. (2020)

Capsaicinoids and capsinoids are compounds found in peppers that may improve athletic performance. Capsaicin (the compound that makes spicy foods spicy) is the most well-known of these compounds, but other non-spicy compounds may also have positive effects on performance. 9 out of 14 animal studies and 5 out of 8 human studies have found that these compounds improve physical performance (some studies have looked at endurance performance, while other have looked at strength or power). The studies are too dissimilar to be worth meta-analyzing, but ~60% of studies finding significant, positive effects represents a pretty strong track record for this class of compounds, though more research is certainly needed. The potential mechanisms by which capsaicinoids and capsinoids may improve performance are summarized in the figure below.

capsaicinoids mechanisms vilton


CYP1A2 genotype and acute ergogenic effects of caffeine intake on exercise performance: a systematic review. Grgic et al. (2020)

CYP1A2 is a gene that codes for the rate-limiting protein in caffeine metabolism. People with the AA genotype (“fast metabolizers”) may experience a larger ergogenic effect from caffeine supplementation than people with AC and CC genotypes. However, that effect seems to be largest for relatively long-duration cardiovascular exercise. The effects on resistance exercise are smaller and less consistent.


The Effect of Dietary Nitrate Supplementation on Isokinetic Torque in Adults: A Systematic Review and Meta-Analysis. Lago-Rodríguez et al. (2020)

This meta-analysis found that acute nitrate supplementation doesn’t seem to significantly affect isokinetic torque. It should be noted, however, that only 5 studies were included in the analysis, and a lot of the outcomes only had one study. This is definitely an area where more research is needed before we can draw definitive conclusions.

nitrate isokinetic torque


Effects of diet interventions, dietary supplements, and performance-enhancing substances on the performance of CrossFit-trained individuals: A systematic review of clinical studies. Quaresma et al. (2020)

This paper summarizes the findings of 14 studies investigating the effects of various nutrition and supplementation interventions on CrossFit performance. The only intervention that caused significant improvements in performance was sodium bicarbonate supplementation. However, it would probably be excessively hasty to conclude that sodium bicarbonate is the only ergogenic substance for CrossFitters; we just need more research on other potential interventions.


Effect of short- and long-term protein consumption on appetite and appetite-regulating gastrointestinal hormones, a systematic review and meta-analysis of randomized controlled trials. Kohanmoo et al. (2020)

Higher protein intakes seem to suppress hunger and improve appetite regulation acutely (e.g. all else being equal, a higher protein meal promotes greater feelings of fullness and less hunger than a lower protein meal), but over time, people may habituate to the hunger-suppressing and fullness-promoting effects of elevated protein intakes.

protein hunger


Are There Benefits from the Use of Fish Oil Supplements in Athletes? A Systematic Review. Lewis et al. (2020)

Fish oil has a lot of effects on the human body. With that said, ergogenic effects on athletes are fairly inconsistent. Notably, however, fish oil supplementation may improve rates of recovery following muscle damage, but more research is needed.


The Effects of Intermittent Fasting Combined with Resistance Training on Lean Body Mass: A Systematic Review of Human Studies. Keenan et al. (2020)

In the eight human studies to date, intermittent fasting combined with resistance training generally allows for maintenance of lean body mass (7 out of 8 studies). One study observed an increase in lean body mass. Furthermore, most of the studies (5 out of 8) observed a decrease in fat mass, suggesting that subjects were probably in at least a slight caloric deficit.


Effects of Dietary Nitrate Supplementation on Weightlifting Exercise Performance in Healthy Adults: A Systematic Review. San Juan et al. (2020)

Realistically, this body of literature probably wasn’t quite ready for a systematic review, as only four studies met the authors’ inclusion criteria. However, three of the four studies found that nitrate supplementation successfully improved measures of resistance exercise performance (power, velocity, and reps-to-failure performance). Thus, the literature on nitrate is promising, but we need more studies before drawing any solid conclusions.


The effect of fish oil supplementation on the promotion and preservation of lean body mass, strength, and recovery from physiological stress in young, healthy adults: a systematic review. Heileson and Funderburk (2020)

Fish oil supplementation may help with preserving strength and power performance following muscle damage or immobilization, and it may support the recovery of performance following muscle damage or immobilization, but it doesn’t seem to improve performance chronically or have a notable effect on lean body mass in healthy, young adults.


Acute Effects of Citrulline Supplementation on High-Intensity Strength and Power Performance: A Systematic Review and Meta-Analysis. Trexler et al. (2019)

Citrulline supplementation has a small but significant effect on strength and power endurance tests (e.g. reps to failure tests, or similar challenges). The effect may be larger for strength endurance than power endurance.


Acute Ketone Supplementation and Exercise Performance: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Valenzuela et al. (2019)

Ketone supplementation doesn’t seem to improve exercise performance in tests ranging for short sprints to ~50 minute endurance tests.


Antioxidants for preventing and reducing muscle soreness after exercise: a Cochrane systematic review. Ranchordas et al. (2020)

Antioxidant supplementation seems to attenuate muscle soreness up to 72 hours post-training, but the magnitude of the effect probably isn’t large enough to be practically relevant.


Does Beef Protein Supplementation Improve Body Composition and Exercise Performance? A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Valenzuela et al. (2019)

The effects of beef protein supplementation on strength and muscle growth seem to be similar to the effects of whey protein supplementation.


Effect of Betaine on Reducing Body Fat—A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Xiang et al. (2019)

Betaine (TMG) supplementation may increase body fat reductions, especially when combined resistance training. This study was previously discussed in more depth in MASS.


Effect of Caffeine Supplementation on Sports Performance Based on Differences Between Sexes: A Systematic Review. Mielgo-Ayuso et al. (2019)

Caffeine seems to have similar effects on aerobic performance in both males and females, but it may have larger effects on anaerobic and resistance training performance in males.


Effect of Overnight Fasted Exercise on Weight Loss and Body Composition: A Systematic Review and Meta-Analysis. Hackett and Hagstrom (2017)

Exercise following an overnight fast doesn’t seem to produce more weight loss or more favorable changes in body composition than exercise performed in a fed state. However, there aren’t many studies to analyze (only 5), so these findings should be interpreted with caution due to low statistical power.


Effects of Arginine Supplementation on Athletic Performance Based on Energy Metabolism: A Systematic Review and Meta-Analysis

In a meta-analysis covering 15 published studies, arginine supplementation was found to significantly enhance both aerobic and anaerobic performance outcomes, with effect sizes (Hedges’ g) of 0.84 and 0.24, respectively. However, it appears as if the analysis neglected to account for the inclusion of multiple correlated outcomes from single studies, included the Harvard step test as a measurement of “performance,” included a study that combined arginine with another ingredient (which violated the exclusion criteria), and included at least a few miscalculated effect sizes. More importantly, there just isn’t a reason to supplement with arginine; oral citrulline supplementation increases blood arginine levels more effectively than oral arginine supplementation, and oral citrulline is widely accessible, similarly priced, tastes better, and has more evidence supporting its efficacy.


Effects of Curcumin Supplementation on Sport and Physical Exercise: A Systematic Review. Suhett et al. (2020)

“Eleven papers were selected for this review. Most of the studies displayed positive effects of the curcumin supplementation for athletes and physical exercise practitioners, and no side effects were reported. Participants supplemented with curcumin displayed reduced inflammation and oxidative stress, decreased pain and muscle damage, superior recovery and muscle performance, better psychological and physiological responses (thermal and cardiovascular) during training and improved gastrointestinal function. Curcumin supplementation appears to be safe and beneficial for sport and physical exercise in human beings.” Another 2020 systematic review had similar findings.


Effects of Ramadan Fasting on Physical Performance: A Systematic Review with Meta-analysis. Abaïdia et al. (2020)

Most aspects of physical performance are maintained fairly well during Ramadan fasting, but mean and peak power during Wingate tests (maximal anaerobic tests) significantly decrease. I imagine resistance training work capacity (or any long-duration activity that could be constrained by hydration) would be reduced as well, but there’s not sufficient research on that topic yet.


Effects of Sodium Bicarbonate Supplementation on Muscular Strength and Endurance: A Systematic Review and Meta-analysis. Grgic et al. (2020)

Sodium bicarbonate (baking soda) supplementation significantly increases strength endurance but not maximal strength.


Effects of vitamin C on oxidative stress, inflammation, muscle soreness, and strength following acute exercise: meta-analyses of randomized clinical trials. Righi et al. (2020)

Vitamin C supplementation may reduce some markers of exercise-induced oxidative stress (lipid peroxidation) and inflammation (IL-6), but doesn’t seem to affect the recovery markers most lifters would actually care about (soreness or strength recovery).


Impact of anthocyanin-rich whole fruit consumption on exercise-induced oxidative stress and inflammation: a systematic review and meta-analysis. Bloedon et al. (2019)

Eating a diet high in anthocyanin-rich fruits (such as blueberries and tart cherries) may reduce oxidative stress and inflammation following exercise. Another recent meta (Doma et al., 2020) had broadly similar findings. Another recent systematic review (Ortega et al., 2020) looked at tart cherry and pomegranate juice supplementation. The authors of the review conclude that higher total doses of phenolic compounds (at least 1000mg/day) and longer supplementation durations (beginning several days before strenuous exercise, and continuing through the recovery period) are more likely to have a positive effect. In other words, simply consuming anthocyanin-rich fruits or fruit supplements once before or after a workout may not have much of an effect; you need to consume them consistently, in high enough dosages, for the effect to be consistent and noticeable.


Nicotine effects on exercise performance and physiological responses in nicotine‐naïve individuals: a systematic review. Johnston et al. (2017)

There are plausible mechanisms by which nicotine could improve exercise performance, but placebo-controlled studies don’t reliably report performance benefits from nicotine supplementation for nicotine-naïve individuals.


Omega-3 Polyunsaturated Fatty Acid Supplementation for Reducing Muscle Soreness After Eccentric Exercise: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Zheng-tao et al. (2020)

Omega-3 supplementation significantly reduces muscle soreness following eccentric exercise, but doesn’t seem to improve strength recovery. However, the reduction in muscle soreness, while statistically significant, likely isn’t large enough to be clinically relevant.


Protein Intake Greater than the RDA Differentially Influences Whole-Body Lean Mass Responses to Purposeful Catabolic and Anabolic Stressors: A Systematic Review and Meta-analysis. Hudson et al. (2020)

Protein intakes that exceed the RDA (0.8g/kg per day) increase lean mass gains following resistance training, and attenuate lean mass losses following energy restriction. However, eating more protein probably won’t help you gain more lean mass when you’re in an isocaloric state and you aren’t resistance training.


Supplementation of Probiotics and Its Effects on Physically Active Individuals and Athletes: Systematic Review. Möller et al. (2018)

“Following probiotic supplementation, positive effects have been reported for several outcomes including respiratory tract infection, immunologic markers, and gastrointestinal symptoms in both athletes and nonathletes. However, published studies have distinct protocols and measured outcomes, and some of them have small sample size and failed to prove beneficial effect on probiotic supplementation, leading to inconclusive results for standardized supplementation protocols.”


The Effect of L-Carnitine Supplementation on Exercise-Induced Muscle Damage: A Systematic Review and Meta-Analysis of Randomized Clinical Trials. Yarizadh et al. (2020)

L-Carnitine supplementation may attenuate some markers of muscle damage, but the overall body of literature is still pretty small and findings are reasonably inconsistent. This study was previously discussed in more depth in MASS.


The Effects of Alcohol Consumption on Recovery Following Resistance Exercise: A Systematic Review. Lakićević. (2019)

Alcohol consumption post-exercise may increase cortisol, and decrease testosterone, plasma amino acids, and protein synthesis to some degree. Other markers of physiological function and recovery seem to be largely unaffected. As with anything else, the dose makes the poison; moderate drinking (1-2 standard drinks) probably won’t have a notable effect, while heavy drinking is likely to impair recovery and training adaptations to some degree.


Do multi-ingredient protein supplements augment resistance training-induced gains in skeletal muscle mass and strength? A systematic review and meta-analysis of 35 trials. O’Bryan et al. (2018)

Multi-ingredient protein supplements generally increase fat free mass and strength gains relative to placebo. However, they don’t tend to significantly outperform plain old protein supplements. With that being said, the mean effect for fat free mass leans slightly in favor of multi-ingredient supplements over plain protein supplements, likely due to the inclusion of creatine.


A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. Morton et al. (2018)

Protein supplementation was found to increase gains in both strength and muscle but didn’t have a significant effect on bone mineral content. The relative benefits of protein supplementation were (unsurprisingly) larger for hypertrophy than for strength, and were larger for hypertrophy in trained individuals than in untrained individuals. The relative benefits also tended to be larger in young people than in older people. Furthermore, it was found that increases in lean body mass tended to plateau at a protein intake of around 1.6g/kg (0.73g/lb). However, the confidence intervals extended up to 2.2g/kg (1g/lb), making that the “better safe than sorry” protein recommendation. A more recent meta by Wirth et al. confirmed the finding that protein supplementation significantly increases lean body mass, though it did not find that protein supplementation significantly increased handgrip or leg press strength. However, the p-value for leg press strength in young adults was p = 0.06, which is near the classical significance threshold.

Effects of protein supplementation on increases in strength

 

Effects of protein on increases in FFM

 

The effect of protein supplementation on gains in FFM is influenced by age


Dose-response relationship between protein intake and muscle mass increase: a systematic review and meta-analysis of randomized controlled trials. Tagawa et al. (2020)

This meta is more-or-less an update on Morton’s meta, except that it examined the effects of total protein intake, and not just protein supplementation. In people not performing resistance training, the beneficial hypertrophic effects of higher protein intakes may more-or-less cap out at intakes of ~1.3g/kg. For people performing resistance training, higher protein intakes may lead to greater increases in fat-free mass up to intakes exceeding 3g/kg.


The effect of protein timing on muscle strength and hypertrophy: a meta-analysis. Schoenfeld et al. (2013)

This meta-analysis examined the effects of protein intake in the immediate peri-workout window (within an hour before or after training) versus not consuming protein within that window. Protein timing didn’t significantly affect strength gains. Before adjusting for covariates, the timing did significantly increase hypertrophy. However, many studies didn’t match for total protein intake. After adjusting for higher total protein intakes in the groups consuming protein in the peri-workout window, it didn’t seem that timing significantly affected hypertrophy by itself. In other words, downing a protein shake after your workout may lead to more muscle growth if it increases total protein intake, but it probably won’t make too much of a difference otherwise.

Effect of protein timing on strength

 

Effect of protein timing on hypertrophy, after adjusting for total protein intake

Effects of meal frequency on weight loss and body composition: a meta-analysis. Schoenfeld et al. (2015)

This meta-analysis initially found that higher meal frequencies during weight loss were associated with larger decreases in fat mass and body fat percentage, and smaller decreases in fat-free mass. However, those differences were all driven by a single study; when a sensitivity analysis was performed and that study was removed, there was no significant effect of meal frequency on fat mass, body fat percentage, or fat-free mass.


The Effect of Whey Protein Supplementation on the Temporal Recovery of Muscle Function Following Resistance Training: A Systematic Review and Meta-Analysis. Davies et al. (2018)

Protein supplementation was found to increase rate of recovery from training (defined as restoration of muscle function after a training bout). This effect was only significant (p<0.05) for time points <24 hours post-training, and 72 hours post-training; however, effect sizes favored protein supplementation at all time points (g = 0.4-0.7).


Effects of energy-restricted high-protein, low-fat compared with standard-protein, low-fat diets: a meta-analysis of randomized controlled trials. Wycherley et al. (2012)

High protein diets during weight loss contributed to larger decreases in weight, fat mass, and triglycerides, and smaller decreases in fat-free mass compared to lower protein diets. However, of note, the mitigation in FFM loss only applied to studies lasting more than 12 weeks.

High protein diets lead to more fat loss

 

Protein led to more lean mass retention in studies lasting fewer than 12 weeks

The effects of protein supplements on muscle mass, strength, and aerobic and anaerobic power in healthy adults: a systematic review. Pasiakos et al. (2015)

In terms of strength and hypertrophy, Morton (2018) provides a more up-to-date overview of the literature. However, this systematic review also adds another element. Protein supplementation also may increase gains in aerobic and anaerobic power after aerobic or anaerobic training.


Effects of protein supplements on muscle damage, soreness and recovery of muscle function and physical performance: a systematic review. Pasiakos et al. (2014)

In terms of recovery of muscle function, refer to Davies (2018). However, this systematic review also found that protein supplementation tends to decrease soreness and markers of muscle damage after training.


Threshold of Energy Deficit and Lower-Body Performance Declines in Military Personnel: A Meta-Regression. Murphy et al. (2018)

This meta-analysis found that, in military personnel, neither length of time in an energy deficit nor daily energy deficit were independently associated with decreases in lower body strength or power. However, total energy deficit was strongly associated with decreases in lower body strength and power. It’s not clear whether these findings would directly apply to strength or physique athletes trying to cut weight (while military personnel are very active, it’s not like the bulk of their exercise comes from lifting weights), but they’re at least worth taking note of. If they did apply, the implication would be that a quick cut with a large daily energy deficit and a slow cut with a small daily energy deficit would ultimately have similar impacts on performance. This is an area of research that’s been largely ignored in the context of resistance training, unfortunately (this is the only study I’m aware of, and it was pretty poorly controlled).


Does high-carbohydrate intake lead to increased risk of obesity? A systematic review and meta-analysis. Sartorius et al. (2018)

Short answer: No.

Longer answer: In studies looking at high vs. low absolute carbohydrate intake, and in studies looking at high vs. low carbohydrate intake expressed as a percentage of total calorie intake, carb intake was not associated with increased or decreased odds of obesity.

Absolute carbohydrate intake
Carbohydrate intake as a percentage of total calories

The effect of glutamine supplementation on athletic performance, body composition, and immune function: A systematic review and a meta-analysis of clinical trials. Ahmadi et al. (2018)

Glutamine supplementation doesn’t seem to affect any measurable aspect of athletic performance, or any proxy for muscle damage and recovery (i.e creatine kinase). Glutamine supplementation may help a bit with weight loss (which surprised me, honestly). Interestingly, it seemed to nearly lead to a significant increase in fat mass (CI: -0.19-2.22kg), without having any effect on lean mass. This perplexing result can be explained by the fact that one particularly large study measured weight (reporting a decrease) and fat mass (reporting an increase), but didn’t measure lean mass. It had by far the largest weight in the analyses, so it really drove the results. This one study was allowed to have such undue weight because the authors used a fixed-effects model when they should have used a random-effects model. If they used a random effects model, glutamine probably wouldn’t have been found to effect body weight or body composition either.


Do ketogenic diets really suppress appetite? A systematic review and meta-analysis. Gibson et al. (2015)

A surprising outcome in obesity research is that unlike moderate energy-restricted diets, after initial increases, very low energy diets (VLED; < 800 kcal/day) actually reduce hunger (though long-term adherence is problematic). The same claim is made for very low carbohydrate diets (VLCD). This meta analysis assessed appetite response to both VLED and VLCD (< 10 % kcal or < 50 g/day, ad libitum consumption of protein and fat). VLED increased satiety and decreased hunger without changing desire to eat or the anticipated energy that would or could be eaten. VLCD increased satiety and decreased hunger, and also decreased desire to eat.

Very low energy diets vs. baseline

 

Very low carbohydrate diets vs. baseline

Comparison of weight loss among named diet programs in overweight and obese adults: a meta-analysis. Johnston et al. (2014)

This meta-analysis included 48 RCTs in overweight individuals and categorized diets based on whether or not they were lower carbohydrate (< 40% kcal), “balanced macronutrients,” or low fat (< 20% kcal). At diet conclusion, lower carbohydrate were 83% likely to produce the most weight loss and produced significantly more weight loss than balanced macronutrient diets, but not more weight loss than low-fat diets. At 1 year follow up, low-fat diets were most likely (50%) among the three diets to result in the most weight loss retention. Adverse events incidence was higher during low-carbohydrate versus low-fat diets: constipation (68% vs 35%, respectively), headache (60% vs 40%), halitosis (38% vs 8%), muscle cramps (35% vs 7%), diarrhea (23% vs 7%), general weakness (25% vs 8%), and rash (13% vs 0%; P < .006). However, weight loss differences among diets were not clinically meaningful (1-2 kg over 6-12 months), and the authors suggested individuals follow whichever diet they can adhere to.


Weight loss intervention adherence and factors promoting adherence: a meta-analysis. Lemstra et al. (2015)

Supervised weight loss attempts tend to have about 65% higher adherence than unsupervised attempts, and interventions with a social support component tend to have about 29% higher adherence than interventions without a social support component. Furthermore, dietary interventions tend to have about 27% higher adherence than exercise interventions.


Effects of beta-hydroxy-beta-methylbutyrate supplementation on strength and body composition in trained and competitive athletes: A meta-analysis of randomized controlled trials. Sanchez-Martinez et al. (2017)

In trained athletes, HMB supplementation doesn’t seem to significantly affect either strength gains or changes in body composition (fat mass or fat-free mass). A more recent meta-analysis by Holland and colleagues had similar findings.


Effects of beta-hydroxy-beta-methylbutyrate supplementation during resistance training on strength, body composition, and muscle damage in trained and untrained young men: a meta-analysis. Rowlands et al. (2009)

Like the more recent Sanchez-Martinez meta-analysis, HMB still didn’t do anything for trained athletes back in 2009. However, this meta-analysis did find that HMB supplementation significantly increased lower body strength gains in untrained lifters, though it didn’t affect body composition.


Creatine Supplementation and Lower Limb Strength Performance: A Systematic Review and Meta-Analyses. Lanhers et al. (2015)

Creatine supplementation leads to significantly larger strength gains in both the squat and leg press. The effect was larger for squat (8%) than leg press (3%).

Squat
Leg press

Does oral creatine supplementation improve strength? A meta-analysis. Dempsey et al. (2002) and Effect of creatine supplementation on body composition and performance: a meta-analysis. Branch (2003)

Creatine supplementation also significantly increases lean body mass and bench press strength, and generally improves performance in tasks lasting ≤30 seconds. It may also improve performance in some tasks lasting 30-150 seconds. It may not affect biceps curl strength. It seems to be effective in both men and women (though it may be more effective in men), and in both trained and untrained subjects. It doesn’t seem to reliably affect performance for tests lasting >150 seconds.

From Dempsey et al.
From Branch et al.

Effects of Whey Protein Alone or as Part of a Multi-ingredient Formulation on Strength, Fat-Free Mass, or Lean Body Mass in Resistance-Trained Individuals: A Meta-analysis. Naclerio et al. (2016)

While both whey protein and creatine enhance strength gains and hypertrophy independently, they may have even larger effects when taken together.


Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data. Martineau et al. (2017)

Vitamin D supplementation seems to decrease risk of respiratory tract infections by about 20%. The reduction in risk may be larger in people with low vitamin D levels.


Effects of Vitamin D Supplementation on Serum 25-Hydroxyvitamin D Concentrations and Physical Performance in Athletes: A Systematic Review and Meta-analysis of Randomized Controlled Trials. Farrokhyar et al. (2017).

Even though vitamin D supplementation increases blood concentrations of vitamin D, supplementation doesn’t seem to reliably affect physical performance in athletes (though it may increase handgrip strength).


Does Fish Oil Have an Anti-Obesity Effect in Overweight/Obese Adults? A Meta-Analysis of Randomized Controlled Trials. Shichun et al. (2015)

Fish oil supplementation on top of lifestyle modification doesn’t seem to decrease body weight or BMI more than lifestyle modification alone, but it does lead to significantly larger decreases in waist circumference and waist-to-hip ratio.


β-alanine supplementation to improve exercise capacity and performance: a systematic review and meta-analysis. Saunders et al. (2018)

β-alanine supplementation significantly increases performance for tests lasting 1-10 minutes but doesn’t significantly affect performance for tests lasting <1 minute or for tests lasting 10+ minutes. This makes sense given β-alanine’s mechanism of action – increasing muscle carnosine content, to help buffer against pH decreases. Short-duration activities (i.e. lifting) are unlikely to be limited by inadequate cellular buffering, and long-duration activities aren’t going to rely as much on anaerobic metabolism in the first place.

Subgroups from top to bottom: <1 minute, 1-10 minutes, and 10+ minutes

Effects of caffeine intake on muscle strength and power: a systematic review and meta-analysis. Grgic et al. (2018)

Acute caffeine supplementation increases maximal strength and power, though the overall effect is pretty small. The strength increase is more consistent for upper body strength than lower body strength. The average dose of caffeine used was 4.3-6.5mg/kg. A more recent meta-analysis by Ferreira et al. on the same subject had similar findings: caffeine had a statistically significant effect on bench press strength and strength endurance, but not leg press performance (though non-significant differences still leaned in favor of caffeine supplementation).


Effects of protein supplements consumed with meals, versus between meals, on resistance training-induced body composition changes in adults: a systematic review. Hudson et al. (2018)

Consuming protein supplements with meals instead of between meals may be slightly more beneficial for improving body composition. However, due to heterogeity between studies, few actual head-to-head comparisons, and lack of biological plausibility, my hunch is that it doesn’t actually matter too much, as long as you’re eating enough protein.


Effect of BCAA supplementation on central fatigue, energy metabolism substrate and muscle damage to the exercise: a systematic review with meta-analysis. Hormoznejad et al. (2019)

BCAA supplementation does seem to affect perceptions of fatigue, but it may slightly decrease the rate of metabolic fatigue, and could attenuate muscle damage following intense training. However, these results were found relative to inert control supplementation; it’s unclear if BCAA supplementation has any additional effects if someone is already supplementing with or consuming adequate amounts of protein. A 2017 meta-analysis also had broadly similar findings.


Effect of whey protein supplementation on body composition changes in women: a systematic review and meta-analysis. Bergia et al. (2018)

Whey protein supplemention seems to help increase lean mass in women. However, that effect is only significant in studies without resistance training (with resistance training, whey protein doesn’t seem to help women gain additional lean mass), and in studies imposing an energy deficit (whey protein helps women hold on to more lean mass when dieting, but it doesn’t seem to affect lean mass without a calorie deficit). Furthermore, whey protein supplementation doesn’t seem to lead to significantly greater fat loss in women. All mean effects leaned in favor of whey protein supplementation, but most comparisons simply didn’t clear the threshold of statistical significance.


Dietary fiber intervention on gut microbiota composition in healthy adults: a systematic review and meta-analysis. So et al. (2018)

Interventions involving increases in dietary fiber consumption significantly increased the abundance of intestinal bacteria strains that are generally believed to be beneficial (Bifidobacterium and Lactobacillus). Such interventions also increased fecal butyrate concentrations (which is thought to protect against colon cancer). The fibers that had the largest effect on intestinal bacteria were fructans and galacto-oligosaccharides.


Coffee, Caffeine, and Health Outcomes: An Umbrella Review. Grosso et al. (2017)

“Of the 59 unique outcomes examined in the selected 112 meta-analyses of observational studies, coffee was associated with a probable decreased risk of breast, colorectal, colon, endometrial, and prostate cancers; cardiovascular disease and mortality; Parkinson’s disease; and type-2 diabetes. Of the 14 unique outcomes examined in the 20 selected meta-analyses of observational studies, caffeine was associated with a probable decreased risk of Parkinson’s disease and type-2 diabetes and an increased risk of pregnancy loss. Of the 12 unique acute outcomes examined in the selected 9 meta-analyses of RCTs, coffee was associated with a rise in serum lipids, but this result was affected by significant heterogeneity, and caffeine was associated with a rise in blood pressure. Given the spectrum of conditions studied and the robustness of many of the results, these findings indicate that coffee can be part of a healthful diet.”


Effect of Dietary Sugar Intake on Biomarkers of Subclinical Inflammation: A Systematic Review and Meta-Analysis of Intervention Studies. Della Corte et al. (2018)

Fructose doesn’t seem to contribute to systemic inflammation to a greater degree that other dietary sugars (specifically when comparing fructose vs. glucose, and high fructose corn syrup vs. table sugar [sucrose]).


Glycemic impact of non-nutritive sweeteners: a systematic review and meta-analysis of randomized controlled trials. Nichol et al. (2018)

Overall, it doesn’t seem that non-nutritive sweeteners acutely have any meaningful impact on blood glucose, on average. The glycemic impact at some time points seems to be smaller in diabetics, smaller in people with high BMIs, and smaller in older people. By 120 minutes post-consumption, non-nutritive sweeteners significantly decrease blood glucose. All non-nutritive sweeteners seemed to have similar effects on blood glucose. A 2020 meta-analysis by Greyling and colleagues also found that low-energy sweeteners doesn’t have much of an effect on glucose or insulin post-consumption.


Effects of fasted vs fed‐state exercise on performance and post‐exercise metabolism: A systematic review and meta‐analysis. Aird et al. (2018)

Eating before exercise improves long-duration aerobic performance (but not short-duration performance). However, fasted endurance exercise leads to larger post-exercises increases in plasma free fatty acids, and may lead to larger increases in cellular signaling associated with aerobic training adaptations.


Nutritional Interventions to Improve Muscle Mass, Muscle Strength, and Physical Performance in Older People: An Umbrella Review of Systematic Reviews and Meta-Analyses. Gielen et al. (2020)

This umbrella review surveyed the results of 15 systematic reviews examining the effects of various nutritional interventions on elderly subjects. The strongest evidence was in favor of leucine supplementation and protein supplementation combined with resistance training. If you’re interested in nutritional research related to strength, muscle, or physical performance in elderly folks, this would be a good paper to mine for references to use as a jumping-off point.


Miscellaneous

When is knowledge of performance (KP) superior to knowledge of results (KR) in promoting motor skill learning? A systematic review. Oppici et al. (2021)

Toward understanding of coaches’ role in athletes’ eating pathology: A systematic review and ecological application to advance research. Voelker et al. (2021)

Tolerance to Intermittent vs. Continuous Blood Flow Restriction Training: A Meta-Analysis. Sinclair et al. (2021)

The relationships between step count and all-cause mortality and cardiovascular events: A dose–response meta-analysis. Sheng et al. (2021)

The effectiveness of stress regulation interventions with athletes: A systematic review and multilevel meta-analysis of randomised controlled trials. Murdoch et al. (2021)

The effectiveness of pre-performance routines in sports: a meta-analysis. Rupprecht et al. (2021)

The Effect of Resistance Training in Healthy Adults on Body Fat Percentage, Fat Mass and Visceral Fat: A Systematic Review and Meta-Analysis. Wewege et al. (2021)

The Effect of Intensity, Frequency, Duration and Volume of Physical Activity in Children and Adolescents on Skeletal Muscle Fitness: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Wu et al. (2021)

The Calculation, Thresholds and Reporting of Inter-Limb Strength Asymmetry: A Systematic Review. Parkinson et al. (2021)

Systematic review of automatic assessment systems for resistance-training movement performance: A data science perspective. Hart et al. (2021)

Slow and Steady, or Hard and Fast? A Systematic Review and Meta-Analysis of Studies Comparing Body Composition Changes between Interval Training and Moderate Intensity Continuous Training. Steele et al. (2021)

Sleep interventions for performance, mood and sleep outcomes in athletes: A systematic review and meta-analysis. Gwyther et al. (2021)

Reactive Strength Index and its Associations with Measures of Physical and Sports Performance: A Systematic Review with Meta-Analysis. Jarvis et al. (2021)

Myoelectric Activity and Fatigue in Low-Load Resistance Exercise With Different Pressure of Blood Flow Restriction: A Systematic Review and Meta-Analysis. de Queiros et al. (2021)

Motivational Factors and Barriers Towards Initiating and Maintaining Strength Training in Women: a Systematic Review and Meta-synthesis. Vasudevan and Ford (2021)

Metabolomics in Exercise and Sports: A Systematic Review. Khoramipour et al. (2021)

Mental health interventions in non-elite sport: a systematic review and meta-analysis. Sutcliffe et al. (2021)

Low-to-Moderate-Intensity Resistance Exercise Effectively Improves Arterial Stiffness in Adults: Evidence From Systematic Review, Meta-Analysis, and Meta-Regression Analysis. Zhang et al. (2021)

Effects of Strength Training on Blood Pressure and Heart Rate Variability—A Systematic Review. Corso et al. (2021)

Effects of Spaceflight on Musculoskeletal Health: A Systematic Review and Meta-analysis, Considerations for Interplanetary Travel. Comfort et al. (2021)

Effects of resistance training on insulin sensitivity in the elderly: A meta-analysis of randomized controlled trials. Li et al. (2021)

Effects of Resistance Training Methods on Golf Clubhead Speed and Hitting Distance: A Systematic Review. Uthoff et al. (2021)

Effects of Pre-, Post- and Intra-Exercise Hyperbaric Oxygen Therapy on Performance and Recovery: A Systematic Review and Meta-Analysis. Huang et al. (2021)

Effect of vibration foam rolling on the range of motion in healthy adults: a systematic review and meta-analysis. Park et al. (2021)

Effect of Functional Training on Physical Fitness Among Athletes: A Systematic Review. Xiao et al. (2021)

Effect of an Acute Resistance Training Bout and Long-Term Resistance Training Program on Arterial Stiffness: A Systematic Review and Meta-Analysis. Jurik et al. (2021)

Does mental fatigue affect skilled performance in athletes? A systematic review. Sun et al. (2021)

Does exercise affect bone mineral density and content when added to a calorie-restricted diet? A systematic review and meta-analysis of controlled clinical trials. Yazdanpanah et al. (2021)

Do exercise-associated genes explain phenotypic variance in the three components of fitness? a systematic review & meta-analysis. Chung et al. (2021)

Association between Polymorphisms in Vitamin D Pathway-Related Genes, Vitamin D Status, Muscle Mass and Function: A Systematic Review. Krasniqi et al. (2021)

Accuracy in Predicting Repetitions to Task Failure in Resistance Exercise: A Scoping Review and Exploratory Meta-analysis. Halperin et al. (2021)

A Systematic Review Examining the Approaches Used to Estimate Interindividual Differences in Trainability and Classify Individual Responses to Exercise Training. Bonafiglia et al. (2021)

A Comparison of the Effects of Foam Rolling and Stretching on Physical Performance. A Systematic Review and Meta-Analysis. Konrad et al. (2021)

Is resistance training alone an antihypertensive therapy? A meta-analysis. Abrahin et al. (2021)

Daily Step Count and All-Cause Mortality: A Dose–Response Meta-analysis of Prospective Cohort Studies. Jayedi et al. (2021)

A Systematic Review of the Association Between Muscular Fitness and Telomere Length Across the Adult Lifespan. Marques et al. (2021)

Scapular Dyskinesis Is Not an Isolated Risk Factor for Shoulder Injury in Athletes: A Systematic Review and Meta-analysis. Hogan et al. (2020)

Physical therapy interventions for the treatment of delayed onset muscle soreness (DOMS): Systematic review and meta-analysis. Nahon et al. (2021)

Muscle Activity and Activation in Previously Strain-Injured Lower Limbs: A Systematic Review. Presland et al. (2021)

Ghrelin Response to Acute and Chronic Exercise: Insights and Implications from a Systematic Review of the Literature. Ouerghi et al. (2021)

Genetic variations associated with non-contact muscle injuries in sport: A systematic review. Lim et al. (2021)

Current Techniques Used for Practical Blood Flow Restriction Training: A Systematic Review. Bielitzki et al. (2021)

Exercisers’ Affective and Enjoyment Responses: A Meta-Analytic and Meta-Regression Review. de Oliveira Tavares et al. (2021)

Residual force enhancement in human skeletal muscles: A systematic review and meta-analysis. de Campos et al. (2021)

Gamification for the Improvement of Diet, Nutritional Habits, and Body Composition in Children and Adolescents: A Systematic Review and Meta-Analysis. Suleiman-Martos et al. (2021)

The use of real-time monitoring during flywheel resistance training programmes: how can we measure eccentric overload? A systematic review and meta-analysis. Muñoz-López et al. (2021)

The Accumulated Effects of Foam Rolling Combined with Stretching on Range of Motion and Physical Performance: A Systematic Review and Meta-Analysis. Konrad et al. (2021)

Health Outcomes after Pregnancy in Elite Athletes: A Systematic Review and Meta-analysis. Kimber et al. (2021)

Effects of exercise training with blood flow restriction on vascular function in adults: a systematic review and meta-analysis. Pereira-Neto et al. (2021)

Acute Effects of Training Loads on Muscle Damage Markers and Performance in Semi-elite and Elite Athletes: A Systematic Review and Meta-analysis. Simmons et al. (2021)

Benefits of Daytime Napping Opportunity on Physical and Cognitive Performances in Physically Active Participants: A Systematic Review. Souabni et al. (2021)

What Intervention Techniques Are Effective in Changing Positive Affective Variables and Physical Activity? A Systematic Review and Meta-Analysis. Chen et al. (2021)

Effects of genetic variation on endurance performance, muscle strength and injury susceptibility in sports: A systematic review. Appel et al. (2021)

Effects of chronic physical activity on cognition across the lifespan: a systematic meta-review of randomized controlled trials and realist synthesis of contextualized mechanisms. Pesce et al. (2021)

Effect of resistance training with blood flow restriction on muscle damage markers in adults: A systematic review. de Queiros et al. (2021)

Comparisons of calorie restriction and structured exercise on reductions in visceral and abdominal subcutaneous adipose tissue: a systematic review. Abe et al. (2021)

Effect of resistance training with and without caloric restriction on visceral fat: A systemic review and meta-analysis. Khalafi et al. (2021)

Transcriptomic meta-analysis of disuse muscle atrophy vs. resistance exercise-induced hypertrophy in young and older humans. Deane et al. (2021)

Validity and Reliability of Mobile Applications for Assessing Strength, Power, Velocity, and Change-of-Direction: A Systematic Review. Silva et al. (2021)

Utilisation of far infrared-emitting garments for optimising performance and recovery in sport: Real potential or new fad? A systematic review. Bontemps et al. (2021)

The implementation of resistance training principles in exercise interventions for lower limb tendinopathy: A systematic review. Burton and McCormack (2021)

The application of Goal Setting Theory to goal setting interventions in sport: a systematic review. Jeong et al. (2021)

Effects of Regular Physical Activity on the Immune System, Vaccination and Risk of Community-Acquired Infectious Disease in the General Population: Systematic Review and Meta-Analysis. Chastin et al. (2021)

Is Pre-season Eccentric Strength Testing During the Nordic Hamstring Exercise Associated with Future Hamstring Strain Injury? A Systematic Review and Meta-analysis. Opar et al. (2021)

Is Physical Activity Associated with Less Depression and Anxiety During the COVID-19 Pandemic? A Rapid Systematic Review. Wolf et al. (2021)

Does lower-limb asymmetry increase injury risk in sport? A systematic review. Helme et al. (2021)

Changes in Muscle Oxygen Saturation Measured Using Wireless Near-Infrared Spectroscopy in Resistance Training: A Systematic Review. Miranda-Fuentes et al. (2021)

Blood Flow Restriction Training in Patients with Knee Osteoarthritis: Systematic Review of Randomized Controlled Trials. Pitsillides et al. (2021)

A Critical Systematic Review of Current Evidence on the Effects of Physical Exercise on Whole/Regional Grey Matter Brain Volume in Populations at Risk of Neurodegeneration. Hvid et al. (2021)

Effectiveness of resistance exercises in the treatment of rheumatoid arthritis: A meta-analysis. Zhigang and Yi (2021)

Resistance training to reduce resting blood pressure and increase muscle strength in users and non-users of anti-hypertensive medication: A meta-analysis. Polito et al. (2021)

Master athletes have longer telomeres than age-matched non-athletes. A systematic review, meta-analysis and discussion of possible mechanisms. Aguiar et al. (2021)

Association of circulating C-reactive protein and high-sensitivity C-reactive protein with components of sarcopenia: A systematic review and meta-analysis of observational studies. Shokri-mashhadi et al. (2021)

Strength Training versus Stretching for Improving Range of Motion: A Systematic Review and Meta-Analysis. Afonso et al. (2021)

The Effects of Menstrual Cycle Phase on Elite Athlete Performance: A Critical and Systematic Review. Meignié et al. (2021)

The Ability of Exercise to Mitigate Caloric Restriction-Induced Bone Loss in Older Adults: A Structured Review of RCTs and Narrative Review of Exercise-Induced Changes in Bone Biomarkers. Wherry et al. (2021)

Non-local Muscle Fatigue Effects on Muscle Strength, Power, and Endurance in Healthy Individuals: A Systematic Review with Meta-analysis. Behm et al. (2021)

Footwear and Elevated Heel Influence On Barbell Back Squat: a Review. Pangan and Leineweber (2021)

Effects of tissue flossing on the healthy and impaired musculoskeletal system: A scoping review. Konrad et al. (2021)

Effectiveness of treatments for acute and subacute mechanical non-specific low back pain: a systematic review with network meta-analysis. Gianola et al. (2021)

Does adaptive thermogenesis occur after weight loss in adults? A systematic review. Nunes et al. (2021)


Effect of Nordic Hamstring Exercise Training on Knee Flexors Eccentric Strength and Fascicle Length: A Systematic Review and Meta-Analysis. Medeiros et al. (2021)

A Systematic Review of CrossFit® Workouts and Dietary and Supplementation Interventions to Guide Nutritional Strategies and Future Research in CrossFit®. de Souza et al. (2021)

The Association Between Poor Sleep and the Incidence of Sport and Physical Training-Related Injuries in Adult Athletic Populations: A Systematic Review. Dobrosielski et al. (2021)

Investigating sex differences in the accuracy of dietary assessment methods to measure energy intake in adults: a systematic review and meta-analysis. McKenzie et al. 2021

Heat and Cold Therapy Reduce Pain in Patients with Delayed Onset Muscle Soreness: A Systematic Review and Meta-Analysis of 32 Randomized Controlled Trials. Wang et al. (2021)

This meta-analysis found that post-exercise heat and cold therapy can both reduce muscle soreness assessed within 24 hours after the exercise session, but only heat therapy (particularly the use of hot packs) reduced soreness assessed more than 24 hours post-exercise. However, it’s worth noting that there were not statistically significant differences between heat and cold therapy. Given that cold therapy may reduce muscle growth, and heat therapy is at least as effective for reducing soreness, heat therapy may be a better option if you want to reduce soreness post-training.


The Validity and Reliability of Commercially Available Resistance Training Monitoring Devices: A Systematic Review. Weakley et al. (2021)

The current research examining the validity and reliability of commercial devices used for measuring velocity and power output in the gym is of fairly low quality overall, but it suggests that linear position transducers (the devices that have a string that attaches to the barbell; GymAware, SmartCoach, 1080Q, T-Force, Chronojump, Tendo, Virtuve, Fitronic, Open Barbell System, and Ergotest) generally perform better than the other types of devices on the market (accelerometers, mobile apps, and optic devices).


Effects of Bilateral and Unilateral Resistance Training on Horizontally Orientated Movement Performance: A Systematic Review and Meta-analysis. Moran et al. (2020)

Bilateral and unilateral training seem to have similar effects on gains in horizontal-oriented performance (sprinting, various agility tests, stair climb speed, etc.). Importantly, plyometric training seems to be key for maximizing horizontal performance. Plyometrics had the largest effect on horizontal performance during unilateral training, and combined training (plyometrics plus resistance training) had the largest effect during bilateral training.

moran speed


Aging and Recovery After Resistance-Exercise-Induced Muscle Damage: Current Evidence and Implications for Future Research. Fernandes et al. (2020)

The key takeaway of this systematic review is that, by and large, older (~40-75 years old) and younger (<30 years old) don’t massively differ in their recovery responses following a resistance training session. However, it’s worth noting that a lot of the exercise protocols used in the research to this point have lacked ecological validity and, quite frankly, any significant degree of difficulty (for example, 6 sets of 5 eccentric reps at 40% of MVIC). If we use a “vote-counting” approach, older people seem to show signs of greater muscle damage and slower recovery (4 studies report that finding, 2 studies report greater damage or slower recovery in younger subjects, and the rest report no difference), and I personally suspect the current literature underestimates how large the differences would be with ecologically valid training protocols. However, the current evidence suggests that, at minimum, there’s not a completely night-and-day difference in recovery capacity between older and younger lifters.


Effects of Testosterone Supplementation on Sarcopenic Components in Middle-Aged and Elderly Men: A Systematic Review and Meta-Analysis. Parahiba et al. (2020)

I’m sure this comes as a surprise to no one, but exogenous testosterone supplementation tends to increase lean mass and strength.


The Impact of Sleep Duration on Performance Among Competitive Athletes: A Systematic Literature Review. Kirschen et al. (2020)

In general, sleep extension tends to improve athletic performance, while sleep restriction or deprivation tends to decrease performance. Those effects seem to be larger and more consistent for aspects of athletic performance that require focus or active thought (strategy, coordination, etc.) rather just sheer physiological capacity (strength, endurance, etc.). Additionally, longer-term interventions (lasting a few days or weeks rather than just one night) are more likely to find positive effects from sleep extension and negative effects from sleep restriction, including effects on physiological capacity.

This study was reviewed in more depth in the November 2020 issue of MASS.


Acute Effects of Cluster and Rest Redistribution Set Structures on Mechanical, Metabolic, and Perceptual Fatigue During and After Resistance Training: A Systematic Review and Meta-analysis. Jukic et al. (2020)

Cluster set training and rest redistribution training (which is basically the same thing as cluster set training) help people better-maintain velocity and power output during resistance training, while also reducing lactate accumulation and perceived effort.

cluster sets


Effects of Resistance Training on Muscle Size and Strength in Very Elderly Adults: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Grgic et al. (2020)

This meta was basically interested in investigating whether very old people (at least 75 years old) were still capable of getting stronger and building muscle. They are. The pooled effect size for strength was quite large (0.97), while the pooled effect size for hypertrophy was considerably smaller (0.30). The authors also report that resistance training didn’t cause a significant increase in grip strength, though I’d take that lack of significance with a grain of salt; the confidence interval barely crossed zero (ES = 0.25; 95% CI = -0.02-0.54; p = 0.064), and all point estimates leaned in favor of resistance training improving grip strength. They also report no significant fiber hypertrophy, though I’d also take that outcome with a grain of salt, since only 3 studies measured fiber hypertrophy (and again, all point estimates leaned in favor of resistance training).

Another recent meta by Straight and colleagues also examined fiber hypertrophy in older adults (age range: 59-88.5 years old). It found significant type I and type II fiber hypertrophy in older adults, with rates of hypertrophy tending to be lower for older subjects. However, age only explained a small proportion of the variance (~11%), suggesting that new lifters should still be able to experience some degree of hypertrophy into their 80s (though people in the 50s and 60s will generally experience more hypertrophy).

grgic elderly strength

Grgic elderly hypertrophy


The Muscle Carnosine Response to Beta-Alanine Supplementation: A Systematic Review and Bayesian Individual and Aggregate Data E-Max Model and Meta-analysis. Rezende et al. (2020)

This was an interesting meta-analysis. It was interested in the maximum possible increase in muscle carnosine content following beta-alanine supplementation. The authors propose that muscle carnosine levels may be able to almost double following sufficient beta-alanine supplementation, but that most research protocols only provide enough beta-alanine supplementation to increase muscle carnosine levels by ~30%. They suggest that a cumulative dose of ~1500+g of beta-alanine would be required to maximize muscle carnosine levels. At the standard dose of 6.4g/day, it would, therefore, take approximately 8 months to maximize muscle carnosine levels, whereas lead-in times for many studies last only 4 weeks. If the authors’ model is accurate, the possible ergogenic effect of beta-alanine supplementation may be considerably larger than the current literature suggests, but studies with longer lead-in periods or larger daily beta-alanine doses would be required to confirm this hypothesis.

stronger by science carnosine


Does Acupuncture Benefit Delayed Onset Muscle Soreness after Strenuous Exercise? A Systematic Review and meta-analysis. Chunwei et al. (2020)

Acupuncture may improve recovery (soreness, isometric force, and creatine kinase) for up to 72 hours post-training. However, the majority of the studies included in this meta compared acupuncture to a no-treatment control condition, not a sham treatment. As such, it’s hard to know the degree to which these effects are driven by acupuncture itself, versus a simple placebo effect.


Core Muscle Activity during Physical Fitness Exercises: A Systematic Review. Olivia-Lozano and Muyor (2020)

This is a systematic review of 67 studies examining muscle activity in 6 different muscles, so it would be virtually impossible to succinctly summarize. However, if you’re interested in learning about how different exercises affect more muscle activation, this would be a useful review to read and mine for references.


A Meta-Analysis of the Effects of Foam Rolling on Performance and Recovery. Wiewelhove et al. (2019)

Foam rolling before exercise seems to have small beneficial effects on sprint performance and flexibility, but not jumping performance or strength. Foam rolling after exercise seems to have a small effect on attenuating acute post-training strength decreases, decreases in sprint speed, and muscle pain perception. The findings of another review were broadly similar.


Acute Effects of Foam Rolling on Range of Motion in Healthy Adults: A Systematic Review with Multilevel Meta-analysis. Wilke et al. (2019)

Foam rolling does acutely improve range of motion, but it doesn’t appear to be any more effective than stretching. Foam rolling may also be a bit more effective for females than males.


Cooling during exercise enhances performances, but the cooled body areas matter: A systematic review with meta‐analyses. Douzi et al. (2019)

Many different cooling interventions during exercise seem to improve aerobic exercise performance. There’s less research on anaerobic exercise, but whole-body cooling garments have some empirical support. This study was previously discussed in more depth in MASS.


Effects of Evening Exercise on Sleep in Healthy Participants: A Systematic Review and Meta-Analysis. Stutz et al. (2018)

On average, as long as you complete your exercise session at least an hour before going to bed, evening exercise shouldn’t have a significant negative impact on sleep.


Effects of local cryotherapy for recovery of delayed onset muscle soreness and strength following exercise-induced muscle damage: systematic review and meta-analysis. Nogueira et al. (2019)

Local cryotherapy (i.e. icing a muscle after you train it) does not seem to be effective for reducing soreness or attenuating strength losses following a training session.


Effects of Prior Cognitive Exertion on Physical Performance: A Systematic Review and Meta-analysis. Brown et al. (2019)

Intense mental exertion before exercise testing generally reduces most measures of physical performance. If possible, it’s probably not a bad idea to chill out and give your brain a break for a while before you work out.


Electromyographic activity in deadlift exercise and its variants. A systematic review. Martín-Fuentes et al. (2020)

This would be a tough review to summarize succinctly. However, it’s a good resource if you want to get a quick overview of the current EMG research on various deadlift varieties.


Including the Nordic hamstring exercise in injury prevention programmes halves the rate of hamstring injuries: a systematic review and meta-analysis of 8459 athletes. van Dyk et al. (2019)

The title of this meta-analysis is shockingly self-explanatory. Nordic curls dramatically decrease the risk of hamstrings strains in athletes.


Is tDCS an Adjunct Ergogenic Resource for Improving Muscular Strength and Endurance Performance? A Systematic Review. Machado et al. (2019)

Transcranial direct current stimulation (tDCS) seems to improve strength and strength endurance performance pretty reliably, but its effects on endurance performance are less reliable. More research is needed to understand how to most reliably elicit positive effects.


Overtraining in Resistance Exercise: An Exploratory Systematic Review and Methodological Appraisal of the Literature. Grandou et al. (2020)

While there’s a lot of research regarding markers and predictors of overtraining in aerobic sports, less total research exists regarding overtraining and resistance exercise. So far, the only reliable marker we know of for identifying overtraining in resistance exercise exercise is a sustained decrease in performance.


Physical Effects of Anabolic-androgenic Steroids in Healthy Exercising Adults: A Systematic Review and Meta-analysis. Andrews et al. (2018)

It should surprise no one to learn that anabolic steroids help people build more muscle and gain more strength. 13 studies reported adverse events, which are summarized below.


The association of resistance training with mortality: A systematic review and meta-analysis. Saeidifard et al. (2019)

Resistance training is associated with a ~20% lower rate of all-cause mortality. The combination of resistance and aerobic training is associated with a ~40% lower all-cause mortality rate. Breaking news: exercise is good.


The effect of exercise interventions on resting metabolic rate: A systematic review and meta-analysis. MacKenzie-Shalders et al. (2020)

Exercise interventions tend to increase your resting metabolic rate by ~70-100kcal/day, on average. The effect is statistically significant for resistance exercise but not aerobic exercise, primarily because the increase seems to be more homogeneous for resistance exercise (CI: 45 – 147kcal/day) than aerobic exercise (CI: -58 – 221kcal/day).


The Effect of the Menstrual Cycle and Oral Contraceptives on Acute Responses and Chronic Adaptations to Resistance Training: A Systematic Review of the Literature. Thompson et al. (2019)

It’s hard to give this systematic review a short summary. However, overall, oral contraceptives may have a slight negative impact on recovery from resistance exercise; their effect on resistance training adaptations is unclear. Female lifters may make slightly faster progress when training in the follicular phase of their menstrual cycle when compared to the luteal phase. It’s hard to make many firm conclusions, however, due to the variety of different oral contraception formulations and relative dearth of studies on the effects the menstrual cycle has on exercise recovery.


The Effects of Oral Contraceptives on Exercise Performance in Women: A Systematic Review and Meta-Analysis. Elliott-Sale et al. (2020)

This meta-analysis found that oral contraceptives may slightly reduce performance in female athletes. The pooled effect sizes were trivial (d = 0.18 when comparing the early follicular phase to the withdrawal phase on OCs, and d = 0.13 when comparing the rest of the menstrual cycle to active pill days on OCs), however. Therefore, oral contraceptives may slightly decrease exercise performance, but the magnitude of the effect is likely too small to be meaningful for most athletes, though the magnitude of the effect likely varies based on the individual and form of OC.


The Placebo and Nocebo effect on sports performance: A systematic review. Hurst et al. (2019)

Placebo and nocebo effects have small but notable effects on sport and exercise performance. The “intensity” of the placebo (i.e. something like placebo steroids are more intense than placebo caffeine supplementation) seems to substantially impact the magnitude of the placebo effect. This study was previously discussed in more depth in MASS.

 


An evidence-based approach for choosing post-exercise recovery techniques to reduce markers of muscle damage, soreness, fatigue and inflammation: a systematic review with meta-analysis. Dupuy et al. (2018)

Several different recovery modalities, including massage, active recovery, compression garments, water immersion, contrast water therapy, and cryotherapy were found to significantly decrease DOMS and attenuate increases in inflammatory markers. Massage was found to be most effective for attenuating both DOMS and perceived fatigue. It’s also worth noting that while cold water immersion was found to be effective for promoting recovery, other research shows that it can decrease muscle growth if used chronically. This study was reviewed in more detail in Volume 2, Issue 6 of MASS.


Talent Identification in Sport: A Systematic Review. Johnston et al. (2017)

We don’t actually know very much about talent identification in sport, generally. However, the quality of the research varies sport-to-sport. The research to-date is summarized in Table 1 of the article; there’s too much to provide a tidy synopsis here, but it’s worth reading for yourself if talent identification in a particular sport matters to you.


Blood flow restriction training in clinical musculoskeletal rehabilitation: a systematic review and meta-analysis. Hughes et al. (2017)

Low-load training with blood flow restriction seems to aid in strength recovery after injury better than low-load training without blood flow restriction. However, heavier training was more effective for regaining strength than low-load training with blood flow restriction. If loading is tolerated, heavier training is typically the better option; however, low-load training with blood flow restriction seems to be a better option than plain lo- load training in situations where a tissue isn’t yet ready for heavier loading.


Sleep Interventions Designed to Improve Athletic Performance and Recovery: A Systematic Review of Current Approaches. Bonnar et al. (2018)

Sleep extension (aiming for 9+ hours of sleep per night) was found to most reliably improve performance. Improving sleep hygiene also tended to improve performance, though to a smaller degree and less reliably than sleep extension. This systematic review was discussed in Volume 2, Issue 3 of MASS.


Choking interventions in sports: A systematic review. Gröpel and Mesagno (2018)

“The most reported effective interventions were pre-performance routines, quiet eye training, left-hand contractions, and acclimatisation training. The use of dual task was beneficial for performance under pressure but harmful when used in training. Mixed evidence was found for analogy learning, and null effects were reported for goal setting, neurofeedback training, and reappraisal cues.”


Mindfulness and acceptance approaches to sporting performance enhancement: a systematic review. Noetel et al. (2017)

“Compared to no treatment in randomised trials, large effect sizes were found for improving mindfulness, flow, and performance, and lower competitive anxiety. Evidence was graded to be low quality, meaning further research is very likely to have an important impact on confidence in these effects…A number of studies found positive effects for mindfulness and acceptance interventions; however, with limited internal validity across studies, it is difficult to make strong causal claims about the benefits these strategies offer for athletes.”


Influence of chronic stretching on muscle performance: Systematic review. Medeiros et al (2017)

In 28 studies that examined the effects of chronic stretching on muscular performance, 14 reported increases in performance, while the rest reported no difference (none reported decreases in performance). All of the studies reported improvements in performance used dynamic tests, while no measures of isometric strength improved. This systematic review was discussed in Volume 1, Issue 4 of MASS.


The Effects of Injury Prevention Programs on the Biomechanics of Landing Tasks: A Systematic Review With Meta-analysis. Lopes et al. (2017)

Injury prevention programs aimed at altering biomechanical profiles associated with ACL injury risk seem to be effective. Specifically, they seem to help increase knee and hip flexion angles during landing tasks (meaning people are absorbing force more effectively, rather than getting a big “shock” when they land), and decrease knee abduction moments (knee caving). The fact that landing mechanics are trainable is important information for coaches who train athletes (specifically female athletes in sports that require a lot of jumping).


Effects of creatine supplementation on cognitive function of healthy individuals: A systematic review of randomized controlled trials. Avgerinos et al. (2018)

Creatine supplementation may improve short-term memory and reasoning ability, especially in older adults. The effects on memory are larger in vegetarians than omnivores. Creatine supplementation doesn’t seem to affect other cognitive domains.


The effect of resistance exercise on sleep: A systematic review of randomized controlled trials. Kovacevic et al. (2018)

“Chronic resistance exercise improves all aspects of sleep, with the greatest benefit for sleep quality. These benefits of isolated resistance exercise are attenuated when resistance exercise is combined with aerobic exercise and compared to aerobic exercise alone. However, the acute effects of resistance exercise on sleep remain poorly studied and inconsistent. In addition to the sleep benefits, resistance exercise training improves anxiety and depression. These results suggest that resistance exercise may be an effective intervention to improve sleep quality.”


The epidemiology of injuries across weight-training sports. Keogh and Winwood (2017)

Bodybuilding has the lowest injury risk (0.24-1 injuries per 1,000 hours) and strongman and highland games have the highest injury risk (4.5-7.5 injuries per 1,000 hours), while weightlifting and powerlifting fall in the middle. A more recent meta-analysis by Rodríguez and colleagues looked at injury rates in CrossFitters, finding injury rates comparable to those seen in powerlifters and weightlifters.


Is core stability a risk factor for lower extremity injuries in an athletic population? A systematic review. De Blaiser et al. (2018)

Low core stability may increase athletes’ risk of lower extremity injuries.


Melatonin for the prevention and treatment of jet lag. Herxheimer and Petrie (2002)

Melatonin taken before bed helps you adapt to a new time zone when traveling, reducing symptoms of jet lag. Doses between 0.5mg and 5mg seem to be effective (with 5mg helping more than lower doses), and fast-release pills seem to work better than slow-release pills. While melatonin can help when only crossing a couple time zones, it appears that its effects are most notable when crossing 5+ time zones.


Association of Efficacy of Resistance Exercise Training With Depressive Symptoms: Meta-analysis and Meta-regression Analysis of Randomized Clinical Trials. Gordon et al. (2018)

Resistance training seems to aid in decreasing depressive symptoms. This is rather unsurprising, as exercise in general helps decrease depressive symptoms. However, resistance training seems to work just as well as aerobic training, if not slightly better (“When directly comparing the effects of resistance exercise training and aerobic exercise training, a small, nonsignificant mean effect change favoring resistance exercise training was found”). It’s possible that this meta-analysis overestimates the effects of resistance exercise on depression, however. The authors note that higher-quality studies tended to find smaller (though still positive) effects than lower-quality studies.


Effects of Strength Training on Running Economy in Highly Trained Runners: A Systematic Review With Meta-Analysis of Controlled Trials. Balsalobre-Fernandez et al. (2016)

In really well-trained runners, resistance training (generally a combination of lifting and plyometrics) has a large, beneficial effect on running economy. A 2018 systematic review by Blagrove et al. on trained (but not quite as well-trained) broadly agrees with these findings, adding, “Time trial (TT) performance (1.5–10 km) and anaerobic speed qualities also tended to improve following ST. Other parameters [maximal oxygen uptake (VO2max), velocity at VO2max, blood lactate, body composition] were typically unaffected by ST.” In other words, it appears that strength training primarily improves running performance by increasing speed and running economy, without negatively affecting purely aerobic variables.


A Systematic Review of the Effects of Resistance Training on Body Image. SantaBarbara et al. (2017)

“The majority (8 of 11) of studies concluded that resistance training can significantly improve multiple dimensions of body image, including body satisfaction, appearance evaluation, and social physique anxiety…Overall, resistance training seems to have the potential to improve body image in adults, but future high-quality studies with more rigorous testing methods and study designs are needed.”


Strength training as superior, dose-dependent and safe prevention of acute and overuse sports injuries: a systematic review, qualitative analysis and meta-analysis. Lauersen et al. (2018)

Strength training may reduce the risk of sports injuries by approximately 2/3rds.


Muscle Dysmorphia Symptomatology and Associated Psychological Features in Bodybuilders and Non-Bodybuilder Resistance Trainers: A Systematic Review and Meta-Analysis. Mitchell et al. (2016)

Bodybuilders display greater symptoms of muscle dysmorphia on all aspects of Muscle Dysmorphia Inventory (MDI) than people who lift weights but aren’t competitive bodybuilders. Furthermore, higher levels of muscle dysmorphia were positively associated with increased anxiety, depression, and neuroticism, and negatively associated with self-concept and self-esteem.


In-house meta-analyses

Should You Cut Before You Bulk?: How Body-Fat Levels Affect Your P-Ratio

It’s commonly believed that people with higher levels of body fat will struggle to build muscle (or that building muscle will require a larger caloric surplus, leading to more fat gain per unit of muscle gain). We performed a subject-level meta-analysis, suggesting that’s not the case.

Periodization: What the data say

Periodized training leads to larger strength gains than non-periodized training, and undulating periodized training leads to larger strength gains than linear periodized training. When stratifying by training status, periodized training leads to larger strength gains in both trained and untrained lifters. However, undulating periodized training only leads to larger strength gains in trained lifters, but not untrained lifters. When stratifying by lift, periodized training and undulating periodized training lead to significantly larger bench press strength gains than non-periodized and linear periodized training, respectively. Periodized and periodization style don’t seem to significantly affect squat strength gains.

periodized vs nonperiodized strength gains


Strength training for women: setting the record straight

Relative (%) strength gains tend to be larger in women than in men. When stratifying by age relative strength gains are larger for young women than young men, while relative strength gains aren’t significantly different in older men and women. When splitting upper and lower body strength gains, relative gains in upper body strength are larger for young women than young men, while relative gains in lower body strength aren’t significantly different between sexes. Relative hypertrophy is similar in men and women. Obviously, absolute strength gains and hypertrophy are larger in men.

 

That’s all we’ve got! We’ll update this page as new systematic review and meta-analyses are published. Feel free to bookmark this page and refer back to it when you want to get a quick overview of a given area of research.

If you made it this far, you’re clearly very passionate about staying up-to-date with the latest research in strength, muscle growth, and body composition. You should check out our research review: Monthly Applications in Strength Sport (MASS). Each month, we review the best and most relevant research for strength and physique athletes and coaches, helping you stay on the cutting edge. You can check out a free issue here, if you’re interested.

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