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.

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.

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.

Strength

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.

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.

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.



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.

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



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.

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.

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).

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.

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 (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.

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.

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.

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.

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.

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.

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.

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.

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).

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.

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.

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.).

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.

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.

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 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

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.

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 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.”

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 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.”

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.

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.

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.

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.

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).

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.

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.

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.

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.

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.

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.

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.

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.

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

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.

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.

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.

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.

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

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.

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

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

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.

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.

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.

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

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).

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.



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 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 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.”

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.

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.

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.

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.

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.

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.

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).

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.

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.

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.

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).

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.

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.

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.

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.

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.

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).

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

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.

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

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.

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).

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 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.

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).

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.

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.

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.

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.

“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.”

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]).

Overall, it doesn’t seem that non-nutritive sweeteners actuely 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.

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.

Miscellaneous

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).

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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).

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.

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.

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.

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.

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.

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 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.

“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.”

“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.”

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.

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).

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.

“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.”

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.

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

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.

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.

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

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

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.

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.