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83 Evidence Based Answers to Fitness and Nutrition FAQs

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registered dietitian looking at pizza through a microscope

This science stuff goes over my head…I’m glad there are folks out there who know what they’re doing

Each of the 80+ answers to fitness and nutrition questions that you’ll find below has at least half a dozen studies to back it up (upwards 50 individual studies in some cases).

Let it be known: I, Rob Shoecraft did not grind through the thousands of studies and academic papers that formulate the answers below.  No, Greg, Eric and Mike; the three hyper-intelligent powerlifters who run MASS Research; here’s my review of MASS Research Review) did that “heavy lifting” (get it?) for me.

The bulk of information in the FAQ below came from an epic list of meta-analyses and systematic reviews assembled by Greg Nuckols (be sure to check it out here: Strength and Physique Systematic Review and Meta-Analysis Master List).  It’s just the tip of the iceberg compared to the premium content the guys offer.

If you are a personal trainer, coach, strength sport athlete, or just a fitness geek, I could not recommend a subscription to MASS enough.

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  • Leave the Gym with a Little Left in the Tank
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  • Hormonal Contraceptives Don’t Mitigate Strength Gains
  • Power Training or Speed Work for Some, But Not All?
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Fitness and Nutrition FAQs

My opinion is--at most--anecdotally expressed in this table. The entries in this table simply show what the most recent scientific data say.

* The "Usefulness" score is just a subjective measure that I made up. It takes into account both the quality of the studies in question as well as the general applicability of the findings.
Answer and LinksQuestionCategoryTypeUsefulness (1-4)*
Answer:
Undulating periodization and linear periodization were equally effective in building strength...unless your primary concern is maxing out on the leg press machine, in which case undulation is the winner.

Other details:
Bench press and squat 1 RM were also tested, but didn't show any significant difference between the two modes of periodization.

17 studies (510 participants) were reviewed.

Link to study:
Systematic review and meta-analysis of linear and undulating periodized resistance training programs on muscular strength.
Which is better for building strength: undulating or linear periodization?StrengthMeta-analysis2
Answer:
Yes.

Higher weekly set volume (5-10+ sets) was shown to be more effective at building strength than lower weekly set volume (less than 5 sets). This holds true across the board for compound, as well as isolated joint exercises.

The differences, however, weren't staggering. Higher set volume participants averaged 20% quicker strength gains than their lower set counterparts.

Other details:
The more experienced the individual, the more increased set volume seemed to improve strength gains. That said, noobs didn't see much of an improvement from higher volume.

The answer comes from a review of 9 different studies (185 participants).

Link to study:
The Effect of Weekly Set Volume on Strength Gain: A Meta-Analysis.
Does weekly set volume affect strength gains?StrengthMeta-analysis3
Answer:
Yes.

MASS recognized that there was some bias favoring periodized programs among the studies analyzed. That said, the results were still rather significantly in favor of periodization.

Other details:
Undulating periodization was primarily used.

The 1 rep maxes were tested in squat, bench press and leg press.

Higher frequency training sessions were found to be more effective at improving maximal strength.

Exercise variation was also found to have a greater effect.

18 studies were reviewed.

Link to study:
Comparison of Periodized and Non-Periodized Resistance Training on Maximal Strength: A Meta-Analysis
Is periodized training superior for building strength than non-periodized training?StrengthMeta-analysis3
Answer:
Yes!

Concurrence of both strength training and low-intensity aerobic training resulted in a significant decrease in maximal strength when compared to subjects who performed strength training alone.

It should be noted that both groups got stronger, but focusing on one goal at a time seemed to make a sizable impact.

Other details:
Only lower body strength was significantly effected; upper body (e.g., bench press max) was not. This is likely due to the mode of cardio (i.e., cycling and running).

Running had a larger negative impact on strength gains than cycling

Hypertrophy (muscle building) demonstrated a similar effect, though not to the same degree.

Subjects who practiced concurrent training enjoyed the highest body fat loss.

21 studies were reviewed.

Link to study:
Concurrent training: a meta-analysis examining interference of aerobic and resistance exercises
Does low-intensity cardio combined with resistance training affect strength gains?StrengthMeta-analysis4
Answer:
Yes.

Similar to the research on low-intensity/resistance training concurrence and its effect on strength gains, high-intensity cardio was also shown to negatively affect the rate of strength gains when compared to those subjects who performed resistance training alone.

There are some big caveats, however...

Other details:
High intensity running (i.e., sprints) didn't seem to have a negative effect. Cycling sprints, however, did decrease the rate of strength gains when compared to those who performed running in concurrence with resistance training.

In either case, only lower body strength gains were affected. There were no significant difference in upper body strength in either group (similar to the low-intensity research).

Hypertrophy (muscle building) wasn't significantly affected in either case.

Longer sprint interval rest periods (in both running and cycling) seemed to lessen interference effect of concurrent training.

Meta-analysis was comprised of 13 different studies

Link to study:
The compatibility of concurrent high intensity interval training and resistance training for muscular strength and hypertrophy: a systematic review and meta-analysis
Does high-intensity cardio combined with resistance training affect strength gains?StrengthMeta-analysis3
Answer:
Lifting first.

Those who performed resistance training before their aerobic cardio session enjoyed 7% larger strength gains...not a huge difference, but if you're gonna choose an order, it's a no-brainer...especially considering the following...

Other details:
Aerobic fitness wasn't affected either way.

Body fat loss wasn't affected either way.

Isometric strength wasn't affected either way (how long can you wall sit, bro?).

9 studies were reviewed in this meta-analysis.

Link to study:
The Role of Intra-Session Exercise Sequence in the Interference Effect: A Systematic Review with Meta-Analysis.
Which is better for strength: cardio first or lifting first?StrengthMeta-analysis3
Answer:
Yep, pretty much.

Those who routinely lifted at least 60% of their 1 rep max over the course of 6 weeks enjoyed significantly higher strength gains than those who trained below 60%.

Other details:
Muscle growth (hypertrophy) remained about the same in both groups.

Isometric strength didn't favor one way or the other.

21 studies were researched in this meta-analysis.

Link to study:
Strength and Hypertrophy Adaptations Between Low- vs. High-Load Resistance Training: A Systematic Review and Meta-analysis.
Do you have to lift heavy to get strong?StrengthMeta-analysis4
Answer:
Yes...sorta.

Those who lifted more often during the week (up to 4 times) enjoyed greater strength gains than those who didn't.

That said, in studies where volume was matched to frequency (e.g., 4 sets in one session vs. 4 sets spread throughout the week), the results weren't significantly different.

It seems that volume is the main driver, not necessarily weekly frequency.

Other details:
Upper body strength increased more quickly than lower body strength.

Women benefited more from increased frequency than men.

Young folks benefited more from increased frequency than older subjects in the study.

Most of the subjects were untrained. MASS did a breakdown of the effect of high frequency training among more experienced lifters, which is available among their premium content.

22 studies were included in this meta-analysis.

Link to study:
Effect of Resistance Training Frequency on Gains in Muscular Strength: A Systematic Review and Meta-Analysis
Does training frequency (how often you lift) affect strength gains?StrengthMeta-analysis3
Answer:
Yes, but this study is a little muddy.

The combined research in this analysis shows that there wasn't a significant difference between moderate-to-slow tempo training and fast, high-velocity training. However, many of the studies had the subject performing to failure (I'm not sure why).

When the aforementioned "failure" studies are teased out, strength gains favor the inclusion of high-velocity, explosive training.

Other details:
Similar results were observed among both novice and experienced subjects, as well as young and old trainees.

15 studies were included in this meta-analysis.

Link to study:
Effect of Movement Velocity During Resistance Training on Dynamic Muscular Strength: A Systematic Review and Meta-Analysis
Can velocity training make you stronger?StrengthMeta-analysis2
Answer:
Nope.

There was no meaningful difference in strength gains between those who trained to failure and those who stopped short.

Other details:
The results remained the same between the four studies where volume was controlled and the four studies where it wasn't.

8 studies were included in this meta-analysis.

Link to study:
https://www.ncbi.nlm.nih.gov/pubmed/26666744
Do you have to train to failure to maximize strength gains?StrengthMeta-analysis4
Answer:
Yes.

Attaching elastic bands or chains to the barbell while performing lifts (variable or accommodating resistance training; VRT) was shown to make subjects significantly stronger; an average of 11 lbs (5 kg) stronger in one rep max testing than those who trained conventionally.

Other details:
Each study was conducted for at least 7 weeks (for what it's worth, I think two months of solid VRT training is a little overkill, especially in an untrained individual...what do I know though?).

Untrained individuals didn't experience as much of a difference in strength gains as more experienced lifters who employed VRT.

7 studies and 235 participants were researched for the meta-analysis.

Link to study:
Effects of Variable Resistance Training on Maximal Strength: A Meta-Analysis.
Does lifting with bands and chains really make you stronger?StrengthMeta-analysis4
Answer:
No.

The study didn't find a significant difference between the two.

Other details:
MASS noted that the lack of data among the included studies was insufficient to form conclusive evidence one way or the other.

7 studies and 71 participants were researched for this meta-analysis.

Link to study:
Is inertial flywheel resistance training superior to gravity-dependent resistance training in improving muscle strength? A systematic review with meta-analyses
Is flywheel equipment better for strength training than free weights or traditional machines?StrengthMeta-analysis1
Answer:
Olympic weightlifting and plyometric training equally improved the counter movement vertical jump test.

The study didn't find a significant difference between the two, however, it did find that both were superior to traditional resistance training (e.g., squats, leg press, etc) in jump performance testing.

Other details:
7 studies included in this meta-analysis.

Link to study:
Effects of weightlifting exercise, traditional resistance and plyometric training on counter-movement jump performance
Which is more effective at improving vertical jump height?: oly weightlifting, traditional resistance training, or plyo training?StrengthMeta-analysis3
Answer:
Nope.

Other Details:
The studies researched in this meta-analysis were simulating high altitude using hypoxic environmental chambers.

It's MASS' opinion that the data on this topic are are bit premature for a meta-analysis.

Link to study:
The efficacy of resistance training in hypoxia to enhance strength and muscle growth: A systematic review and meta-analysis
Does training at a high altitude increase strength gains?StrengthMeta-analysis1
Answer:
Yes!.

This study found that motor imagery training (visualization) led to significantly greater strength gains than no training at all.

Other Details:
There was no significant difference between the combination of physical training and visualization when compared to groups who only physically trained.

That said, MASS noted an additional study which showed that the motor imagery and physical training combination DOES make a significant difference when compared to training alone (Study not included in this meta-analysis: Effects of mental training on muscular force, hormonal and physiological changes in kickboxers)

It's MASS' opinion that this body of research is still in its infancy.

13 articles, consisting of 370 participants were used for the research in this meta-analysis.

Link to study:
Effects and Dose-Response Relationships of Motor Imagery Practice on Strength Development in Healthy Adult Populations: a Systematic Review and Meta-analysis
Can visualization and mental imagery practice aid
strength gains?
StrengthMeta-analysis3
Answer:
Yes!.

Healthy adults 65 and older, benefit greatly from strength training, both in strength gains, as well as muscle morphology.

Other Details:
In short, older adults should train very similarly to younger adults, with the exception of a comparatively slight decrease in volume and intensity.

Here is an image provided by MASS, which breaks down the ideal training variables for strength and muscle gains in senior citizens:
Provided by StrongerbyScience.com

25 studies were evaluated for this meta-analysis.

Link to study:
Dose–Response Relationships of Resistance Training in Healthy Old Adults
Can heavy resistance training help gain strength in healthy older adults?StrengthMeta-analysis4
Answer:
Yes.

Of course, there is no true ideal for everyone, but this study was able to identify ideal ranges with respect to rest periods, training frequency, volume and intensity for strength and muscle gains in youth ages 6-18 years old.

Other Details:
The findings of this meta-analysis are very similar to what MASS considers to be a solid general training approach. The following excerpt surmising the data comes from StrongerbyScience.com:

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

43 studies were used to create this meta-analysis.

Link to study:
Effects and dose–response relationships of resistance training on physical performance in youth athletes
Is their an ideal training regimen youth should follow to get stronger?StrengthMeta-analysis4
Answer:
Yes.

All youth female athletes ages 8-18 enjoyed significant strength gains from strength training.

Other Details:
Girls 15 and older experienced greater strength gains.

Studies lasted between 4 and 16 weeks.

85 studies were referenced in this meta-analysis.

Link to study:
A Meta-Analysis of Resistance Training in Female Youth: Its Effect on Muscular Strength, and Shortcomings in the Literature
Can young female athletes benefit from strength training?StrengthMeta-analysis3
Answer:
No...well...maybe?

Other Details:
Of the 5 studies included in this meta-analysis, only 1 of them tested with a free weight back squat, and it showed results in favor of supramaximal eccentric loading for strength gains.

The other 4 tests were conducted with a leg press machine, which didn't show any significant difference.

It's in MASS' opinion that there isn't enough data available to conclusively call it one way or the other.

Link to study:
Supramaximal Eccentrics Versus Traditional Loading in Improving Lower-Body 1RM
Does supramaximal eccentric loading (lowering negatives greater than your max) lead to greater strength gains?StrengthMeta-analysis2
Answer:
No, there was no significant difference in muscle growth between undulating and linear periodization models.

Other Details:
Many of the participants in these studies were untrained. More research is needed to determine results for trained individuals.

13 studies were used for this meta-analysis.

Link to study:
Effects of linear and daily undulating periodized resistance training programs on measures of muscle hypertrophy
Linear periodization vs daily undulating periodization: is one better than the other for muscle growth?HypertrophyMeta-analysis3
Answer:
Nope, not according to this meta-analysis.

Other Details:
The average length of studies in this meta-analysis was 15 weeks.

Of the 12 studies researched, only 2 of them tested trained individuals. That said, much of this evidence is in support of periodized training vs. non-periodized training in untrained individuals.

Link to study:
Should resistance training programs aimed at muscular hypertrophy be periodized? A systematic review of periodized versus non-periodized approaches
Periodization vs. non-peridiodization: Is one model superior for muscle growth?HypertrophyMeta-analysis3
Answer:
Yes.

Other Details:
Groups were essentially placed into three categories: less than 5 sets, 5 to 9 sets, and more than 10 sets per week. The greater the weekly set volume, the greater the increase in muscle growth (5.4%, 6.6%, and 9.8% respectively).

MASS noted that an outlier threw off the results a bit, but even when controlling for the outlier, the results remained proportionally the same.

15 studies were included in this meta-analysis.

They also site an additional meta-analysis, which showed similar results: Single vs. multiple sets of resistance exercise for muscle hypertrophy

Link to study:
Dose-response relationship between weekly resistance training volume and increases in muscle mass
Can more volume per week increase muscle mass?HypertrophyMeta-analysis3
Answer:
No, not significantly anyway.

Other Details:
Technically, eccentric focused training over 6 week minimum cycle resulted in greater gains, however--as noted--the results weren't significant.

MASS sites a Douglas et al. systematic review as a valuable read for further information on the subject.

15 studies were examined in this meta-analysis.

Link to study:
Hypertrophic Effects of Concentric vs. Eccentric Muscle Actions
Does more eccentric focused training lead to greater gains in muscle mass?HypertrophyMeta-analysis3
Answer:
Yes, for lower body.

Upper body was not found to be affected. It's hypothesized that this was due to the aerobic training modalities used for the studies (i.e., cycling and running).

Other Details:
Running had a much greater negative impact on hypertrophy than cycling.

The image below (from StrongerbyScience.com) shows the differences in lower body hypertrophy, strength, power, as well as V02max and body fat among modalities:

from StrongerbyScience.com

21 studies were examined for this meta-analysis.

Link to study:
Concurrent training: a meta-analysis examining interference of aerobic and resistance exercises
Does concurrent aerobic/low intensity training negatively impact muscle gains?HypertrophyMeta-analysis4
Answer:
Nope, no significant differences in upper body and lower body hypertrophy were determined.

Other Details:
Lower body strength (also measured) was effected by high intensity cycling, but not high-intensity running. Long rest periods between intervals seemed to have less of an impact on lower body strength among the cycling participants.

StrongerbyScience.com

Link to study:
The compatibility of concurrent high intensity interval training and resistance training for muscular strength and hypertrophy
Does concurrent high-intensity training have a negative impact on muscle gainsHypertrophyMeta-analysis4
Answer:
No.

The same meta-analysis found that strength was negatively affected when aerobic cardio preceded resistance training, however, hypertrophy seems to be unaffected. According to this study, it doesn't really matter if you do cardio or lift first...for bodybuilding purposes anyway.

Other Details:
10 studies were used in this meta-analysis.

Link to study:
The Role of Intra-Session Exercise Sequence in the Interference Effect
Does cardio before resistance training affect muscle gains?HypertrophyMeta-analysis4
Answer:
Nope.

Your tempo doesn't seem to matter much. Intent seems to be a better predictor of muscle growth than rep duration alone. Train like an animal, and you'll look like one (according to this study...which I paraphrased with reckless abandon).

Other Details:
Studies lasted a minimum of 6 weeks.

Reps were tested primarily from .5 seconds to 8 seconds. That said, a 10+ second rep range was also included in one of the studies. For the latter study, it was found that the ridiculously slow tempo actually negatively affected strength gains, however, the author admits that there isn't quite enough data to stand behind that conclusively.

8 studies were examined for this meta-analysis.

Link to study:
Effect of repetition duration during resistance training on muscle hypertrophy
Does slowing down rep tempo lead to more muscle growth?HypertrophyMeta-analysis4
Answer:
No.

Populations who trained at or above 60% 1RM, and those who trained below both experienced virtually the same results in measured hypertrophy.

Other Details:
One huge additional detail is that both groups trained to failure. In my non-scientifically trained opinion, that says a lot about training to failure its relevance to muscle growth.

The same meta-analysis found that maximal strength improved at a faster rate in the heavier lifting groups.

21 studies were examined for this meta-analysis.

Link to study:
Strength and Hypertrophy Adaptations Between Low- vs. High-Load Resistance Training
Does using heavier weights lead to greater muscle mass?HypertrophyMeta-analysis4
Answer:
Yes.

The results showed that groups who trained twice a week experienced nearly twice the muscular gains that the once per week group experienced.

Other Details:
Unfortunately, there isn't much information in this study on training with even more frequency (>2 times/week)....few subjects trained for 3 days/week.

The same meta-analysis found that maximal strength improved at a faster rate in the heavier lifting groups.

Subjects trained for a minimum of 4 weeks in these studies.

10 studies were compared for this meta-analysis.

Link to study:
Effects of Resistance Training Frequency on Measures of Muscle Hypertrophy
Does training a muscle group more than once a week lead to greater muscle gains?HypertrophyMeta-analysis3
Answer:
Yes...well...no...well, it depends.

Other Details:
Reps lasting 2-3 seconds (slow velocity) resulted in more quad growth in 2 studies, where high velocity reps (1 second) resulted in more bicep growth in 2 studies. All other studies found no difference between either.

It is in MASS' opinion that there isn't yet enough data to really draw any conclusions.

Link to study:
Effect of movement velocity during resistance training on muscle-specific hypertrophy
Does rep velocity affect muscle growth?HypertrophyMeta-analysis2
Answer:
Nope.

Other Details:
The studies researched in this meta-analysis were simulating high altitude using hypoxic environmental chambers.

It's MASS' opinion that the data on this topic are are bit premature for a meta-analysis.

Link to study:
The efficacy of resistance training in hypoxia to enhance strength and muscle growth: A systematic review and meta-analysis
Does training at a high altitude increase the rate of muscle growth?HypertrophyMeta-analysis1
Answer:
Yeh...but who actually knows?

Both populations; those who rested 20-60 seconds between sets, and those who rested >60 seconds experienced increased muscle mass, but those who rested longer experienced significantly more.

That said, the authors of the meta-analysis don't think there's enough data available yet to support either side conclusively.

Other Details:
Participants in each study trained for at least 4 weeks.

6 studies were used in this meta-analysis.

Link to study:
The effects of short versus long inter-set rest intervals in resistance training on measures of muscle hypertrophy
Does rest time in between sets affect muscle growth?HypertrophyMeta-analysis2
Answer:
Yes!.

Healthy adults 65 and older, benefit greatly from strength training, both in strength gains, as well as muscle morphology.

Other Details:
In short, older adults should train very similarly to younger adults, with the exception of a comparatively slight decrease in volume and intensity.

Here is an image provided by MASS, which breaks down the ideal training variables for strength and muscle gains in senior citizens:
Provided by StrongerbyScience.com

25 studies were evaluated for this meta-analysis.

Link to study:
Dose–Response Relationships of Resistance Training in Healthy Old Adults
Does heavy resistance training benefit muscle growth in healthy older adults?HypertrophyMeta-analysis4
Answer:
Yes!

Those who supplemented with more protein enjoyed larger gains in muscle growth.

Other Details:
They also got stronger, though the differences were significantly greater in measures of muscle growth.

Trained individuals saw greater gains from protein supplementation than untrained.

Benefits of protein supplementation tended to be greater in younger people, when compared to older populations.

Benefits typically plateaued at protein consumption of ~1.6g/kg or .73g/lb of body weight, but some plateaus reached 2.2g/kg or 1g/lb of body weight.

Men were primarily studied in this meta-analysis.

49 studies and 1863 participants were researched for this meta-analysis.

Link to study:
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
Does protein supplementation improve gains in muscle growth?NutritionMeta-analysis4
Answer:
Yes.

Those who supplemented with more protein enjoyed larger gains in strength.

Other Details:
They also gained muscle; in fact, differences were significantly greater in measures of muscle growth than in strength.

Trained individuals saw greater gains from protein supplementation that untrained.

Benefits of protein supplementation tended to be greater in younger people, when compared to older populations.

Benefits typically plateaued at protein consumption of ~1.6g/kg or .73g/lb of body weight, but some plateaus reached 2.2g/kg or 1g/lb of body weight.

Men were primarily studied in this meta-analysis.

49 studies and 1863 participants were researched for this meta-analysis.

Link to study:
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
Does protein supplementation improve gains in strength?NutritionMeta-analysis4
Answer:
No.

Other Details:
However, those who supplemented with more protein enjoyed larger gains in muscle growth and strength gains.

49 studies and 1863 participants were researched for this meta-analysis.

Link to study:
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
Does protein supplementation improve gains in bone density?NutritionMeta-analysis3
Answer:
Yes.

Benefits typically plateaued at protein consumption of ~1.6g/kg or .73g/lb of body weight, but some plateaus reached 2.2g/kg or 1g/lb of body weight.

Other Details:
Trained individuals saw greater gains from protein supplementation that untrained.

Benefits of protein supplementation tended to be greater in younger people, when compared to older populations.

49 studies and 1863 participants were researched for this meta-analysis.

Link to study:
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
Is there an ideal amount of protein consumption for muscle growth?NutritionMeta-analysis4
Answer:
Yes, no, and maybe not

These studies compared those who consumed protein within an hour of resistance training to those who did not.

On initial testing, those who consumed protein within the one hour "window of gains" enjoyed greater hypertrophy, but no difference in strength.

However, it was found that the studies didn't match for total protein consumption. Once those calculations were taken into account, the results didn't seem to be significantly different as long as the subjects consumed a matched amount protein during the rest of the day.

Other Details:
20 studies were used for the strength group, and 23 for the hypertrophy group.

Link to study:
The effect of protein timing on muscle strength and hypertrophy
Does protein timing after your workout really make a difference in strength and muscle growth?NutritionMeta-analysis4
Answer:
Yes, according to this meta-analysis, but in actuality...probably not.

At first glance the data show that significant fat loss occurred in the populations who ate smaller meals more frequently.

HOWEVER, upon further analysis, it was shown that nearly all of the supporting data came from a single study. When that study was removed, it was shown that there was no difference between the groups.

Other Details:
15 studies were used for this meta-analysis.

Link to study:
https://www.ncbi.nlm.nih.gov/pubmed/26024494
Does daily meal frequency affect fat loss / body composition?NutritionMeta-analysis3
Answer:
Yes.

Beneficial small to medium effects for whey protein supplementation groups were seen from less than 24 hours all the way through a 96 hours period.

Other Details:
Recovery benefits were most notably observed at the <24 hour and 72 hour marks.

8 studies were used for this meta-analysis.

Link to study:
https://www.ncbi.nlm.nih.gov/pubmed/29462923
Does protein supplementation affect recovery time?NutritionMeta-analysis4
Answer:
Yes!

Participants who consumed high protein, low fat diets lost more overall weight and fat, preserved more fat free mass (FFM) and improved triglyceride levels when compared to those who ate standard protein, low fat diets.

Other Details:
"Changes in fasting plasma glucose, fasting insulin, blood pressure, and total, LDL, and HDL cholesterol were similar across dietary treatments." [1]

"Greater satiety with HP was reported in 3 of 5 studies." [1]

24 trials and 1063 participants made up this meta-analysis.

Link to study:
[1] Effects of energy-restricted high-protein, low-fat compared with standard-protein, low-fat diets
Can eating a high protein diet aid in fat loss?NutritionMeta-analysis4
Answer:
Yeh, probably

There's probably not enough data yet, especially with regard to trained subjects (most of the subject in these studies were untrained...shocker...) to draw any conclusions, but protein supplementation seems to improve both anaerobic and aerobic power output.

Other Details:
This study also further supported that protein supplementation aids in strength and hypertrophy gains (though most gains didn't occur until after several weeks of consistent training).

38 articles were reviewed for this systematic review.

Link to study:
The effects of protein supplements on muscle mass, strength, and aerobic and anaerobic power in healthy adults
Can protein supplementation aid in power production?NutritionSystematic Review2
Answer:
Yes.

Markers of soreness and muscle damage were observed to be reduced in subjects who consumed protein supplements closely following resistance training.

Other Details:
It's also suggested that the potential ergogenic benefits of protein supplementation may be increased when consumption takes place during a negative energy balance (after you're crushed from a killer workout...bro).

27 articles were reviewed for this systematic review.

Link to study:
Effects of protein supplements on muscle damage, soreness and recovery of muscle function and physical performance
Can protein supplementation reduce soreness after intense resistance training?NutritionSystematic Review3
Answer:
Yes, but timing is everything.

Long term caloric deficit had a negative affect on lower body strength and power performance. Short, daily deficits, however, didn't seem to have any negative effects.

Other Details:
"Predictive equations generated from the meta-regression indicated that, for a zero to small (2%) decline in performance, total EB should be limited to − 5686 to − 19,109 kcal, for an entire operation, whereas total EB of − 39,243 to − 59,377 kcal will result in moderate (7%) to large (10%) declines in performance." [1]

In MASS' opinion, this study was poorly controlled.

Data were used from 9 studies for this meta-regression study.

Link to study:
[1] Threshold of Energy Deficit and Lower-Body Performance Declines in Military Personnel
Do active military personnel lose strength and power from eating less during training?NutritionMeta-Regression2
Answer:
No, not necessarily anyway.

Neither high consumption of carbohydrates (represented as a macro split percentage or as an absolute amount) suggested an increased risk for obesity.

Other Details:
Factors such as activity level, sex, total energy intake, and refined vs. unrefined carbohydrates were not taken into account.

More data is needed in this area for any further conclusiveness.

Link to study:
Does high-carbohydrate intake lead to increased risk of obesity?
Does a high carb diet increase the risk of obesity?NutritionMeta-analysis2
Answer:
Eh...maybe weight loss.

According to this meta-analysis and review, glutamine supplementation played no role in performance, immune health, or muscular gains.

Other Details:
It did seem to aid in weight loss.

47 studies were used for this meta-analysis.

Link to study:
The effect of glutamine supplementation on athletic performance, body composition, and immune function
Is glutamine supplementation good for anything?NutritionMeta-analysis3
Answer:
Yes.

Obese subjects who ate less than 50 grams of carbohydrates per day were found to have a suppressed appetite and expressed less of a desire to eat.

Other Details:
Very low calorie diets (less than 800 calories/day) were also observed, and when compared to moderately low calorie diets, subjects also felt more satiated...you read that right...subjects felt fuller on very low calorie diets.

Link to study:
Do ketogenic diets really suppress appetite?
Can ketogenic diets really suppress appetite?NutritionMeta-analysis4
Answer:
Ehhhh...not really.

Three different "diets" were studied: lower carb (less than 40% of a daily macro split), balanced macronutrients, and low fat (less than 20% of macro split).

Straight to the chase: the authors concluded that the best diet is the one the individual will adhere to (of course, no one will ever listen to this common sense logic).

Having said that...

Other Details:
Lower carb diets (less than 40% of daily macro split) were most likely to produce the greatest initial weight loss (83% of tested obese individuals successfully lost weight).

Low fat and lower carbohydrate were just about even in the initial weight loss success rate; both outperformed the "balanced" group.

Low fat dieters enjoyed the greatest success after 1 year.

Low carb dieters experienced the most adverse symptoms including: constipation, halitosis, headache, cramps, diarrhea, weakness and skin irritations.

All that said, the differences between the three group were not "clinically meaningful" after 6-12 months (all measured within 2-5 lbs of each other).

Link to study:
Comparison of weight loss among named diet programs in overweight and obese adults
Is there a "best diet" for overweight people?NutritionMeta-analysis4
Answer:
Yes!

From MASS:

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.

Other Details:
27 studies were included in this meta-analysis.

Link to study:
Weight loss intervention adherence and factors promoting adherence
Do weight loss (both dietary and exercise) interventions actually make a difference?NutritionMeta-analysis4
Answer:
Nope.

Other Details:
"These results remained constant even analyzing by subgroups (HMB doses, duration of intervention, training level and diet co-intervention)." [1]

SIDE NOTE: A meta-analysis separate from this one by Lanhers et al. found that HMB improves lower body strength in untrained lifters (Effects of beta-hydroxy-beta-methylbutyrate supplementation during resistance training on strength, body composition, and muscle damage in trained and untrained young men).

6 studies were included in this meta-analysis.

Link to study:
[1] Effects of beta-hydroxy-beta-methylbutyrate supplementation on strength and body composition in trained and competitive athletes
Does HMB supplementation aid in strength or hypertrophy?NutritionMeta-analysis3
Answer:
Yes.

Subjects supplementing with creatine enjoyed an 8% increase in the back squat when compared to those not taking the supplement.

Other Details:
It doesn't seem to affect exercises lasting longer than 3 minutes.

60 studies were used for these meta-analyses.

Link to study:
Creatine Supplementation and Lower Limb Strength Performance
Does creatine supplementation improve lower body strength?NutritionMeta-analysis4
Answer:
Yes.

Subjects supplementing with creatine were able to increase the rate of strength development in their bench press when compared to those not supplementing with creatine.

Other Details:
It doesn't seem to affect exercises lasting longer than 150 seconds.

96 papers were used for this meta-analysis.

Link to study:
Effect of creatine supplementation on body composition and performance
Does creatine supplementation improve upper body strength?NutritionMeta-analysis4
Answer:
Yes.

Subjects supplementing with creatine enjoyed only small, however, significantly improved rate of hypertrophy.

Other Details:
96 papers were used for this meta-analysis.

Link to study:
Effect of creatine supplementation on body composition and performance
Does creatine help increase lean body mass (i.e., build muscle)?NutritionMeta-analysis4
Answer:
Yes.

Subjects taking both creatine and whey supplements enjoyed gains in upper body and lower body strength, as well as greater muscle growth with respect to those who didn't supplement with the two.

Other Details:
Studies included were 6-12 week trials.

11 studies and 96 participants were included in this meta-analysis.

Link to study:
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
Does supplementing with whey protein and creatine together have an additional effect on strength and muscle growth?NutritionMeta-analysis3
Answer:
Yes!

Ingesting vitamin D supplements reduced chances of infection by 20% across the board.

Other Details:
Those who are already Vitamin D deficient may enjoy an even greater rate of prevention by supplementing with Vitamin D.

Vitamin D3 and D2 were both used separately among the 25 trials. There didn't seem to be a significant difference between the two in prevention rates.

25 trials and 11321 participants were included in this analysis.

Link to study:
Vitamin D supplementation to prevent acute respiratory tract infections
Can vitamin D supplements help prevent respiratory tract infections?NutritionMeta-analysis4
Answer:
No, probably not.

While the athletes' Vitamin D blood levels increased, physical performance did not.

Other Details:
Grip strength may improve with vitamin D supplementation.

13 randomized trials and 532 athletes were included in this analysis.

Link to study:
Effects of Vitamin D Supplementation on Serum 25-Hydroxyvitamin D Concentrations and Physical Performance in Athletes
Does Vitamin D supplementation improve athletic performance?NutritionMeta-analysis3
Answer:
No, BUT, in my opinion, the results were a lot more interesting!

Overweight participants in the studies did not lose any additional body weight while supplementing with fish oil, compared to those who didn't.

However...

Other Details:
Those supplementing with fish oil lost extra inches off their waistline, and lowered their waist to hip ratio...they didn't "lose weight", but they lost belly fat...that's pretty freakin' radical (scientifically speaking)!

21 studies were included in this meta-analysis.

Link to study:
Does Fish Oil Have an Anti-Obesity Effect in Overweight/Obese Adults?
Does fish oil supplementation aid in weight loss?NutritionMeta-analysis4
Answer:
Yes AND No...it basically depends on the game the athlete is playing.

β-alanine supplementation significantly increased performance and work capacity for bouts of exercise lasting 1-10 minutes.

However, it didn't have any significant impact on bouts less than 60 seconds, or more than 10 minutes.

Other Details:
40 studies and 1461 participants were included in this meta-analysis.

Link to study:
β-alanine supplementation to improve exercise capacity and performance
Can β-alanine supplementation improve athletic performance.NutritionMeta-analysis4
Answer:
Yes.

Those supplementing with caffeine experienced small, however, significant increases in both power and strength.

Other Details:
Upper body strength and power were more significantly improved than lower body.

Subjects took anywhere from 4.3-6.5 mg of caffeine per kg of body weight (which seems like a pretty stout dose to me, and I drink a minimum of half a pot/day).

10 studies were used for the strength analysis, and 10 for the power analysis.

Link to study:
Effects of caffeine intake on muscle strength and power
Can consuming caffeine help boost strength and power?NutritionMeta-analysis3
Answer:
"With" meals...although "between" might be just as good as long as you get enough total protein throughout the day.

While the data show small, but significant improvements in body composition in the subjects who consumed supplements with meals, it's in MASS' opinion that there was too much heterogeneity between the studies to draw a distinct conclusion.

Other Details:
34 randomized control trials were evaluated for this meta-analysis.

Link to study:
Effects of protein supplements consumed with meals, versus between meals, on resistance training–induced body composition changes in adults
What's more effective for muscle growth: protein supplementation with meals or between meals?NutritionMeta-analysis2
Answer:
Yes.

BCAA reduction in soreness and creatine kinase (an inflammation marker) was significantly greater than placebo alone, however, MASS pointed out that protein supplementation was superior to BCAAs in the same measures (as demonstrated by previous studies).

Other Details:
8 studies were evaluated for this meta-analysis.

Link to study:
Branched-chain amino acid supplementation and exercise-induced muscle damage in exercise recovery
Can supplementing with BCAAs reduce soreness?NutritionMeta-analysis2
Answer:
Only sometimes.

The only women observed in these studies who put on lean mass (muscle) were those who were not participating in a resistance training program. Those lifting weights did not gain any additional lean mass with respect to those also lifting, but not supplementing with whey protein.

Other Details:
There is tremendous evidence that shows that men experience significantly greater hypertrophy when supplementing with whey protein (this meta-analysis really shocked me...again, who cares what I think?).

Women who consumed whey protein supplements on a caloric deficit diet were able to hold onto more muscle than those who didn't.

13 randomized control trial were included in this meta-analysis.

Link to study:
Effect of whey protein supplementation on body composition changes in women
Does whey protein supplementation help women gain muscle?NutritionMeta-analysis4
Answer:
Yes.

Dietary fiber intervention increased beneficial (or at least though to be beneficial) strains of intestinal bacteria.

Other Details:
Fructans and galactooligosaccharides were used primarily with dietary fiber intervention.

Consuming additional dietary fiber was also thought to decrease the risk of colon cancer (associated with an increase of fecal butyrate).

64 studies and 2099 participants were included in this meta-analysis.

Link to study:
Dietary fiber intervention on gut microbiota composition in healthy adults
Does dietary fiber benefit gut flora?NutritionMeta-analysis4
Answer:
Oh, Yes! I might go as far as to say it should be part of a healthy diet (as long as you don't have dangerously high blood pressure).

[1] “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.”

Other Details:
112 Meta-analyses and observational were included in this review.

Link to study:
[1] Coffee, Caffeine, and Health Outcomes
Can coffee be part of a healthy diet?NutritionUmbrealla Review4
Answer:
No.

While dietary sugar has been shown to contribute to inflammation (this study lists cardiovascular disease, diabetes, dementia, depression and risk of all-cause mortality as being associated with inflammation), high fructose corn syrup does not appear to increase inflammation markers any more than other sugars.

Other Details:
"As summarized narratively, effects were observed in a small number of studies, but the overall picture is inconsistent, the effect sizes are variable, and the overall quality of meta-evidence is low. Additional evidence from future intervention studies on this topic are needed in order to draw confident conclusions as to the effects of dietary sugar on subclinical inflammation." [1]

...in other words, we need more research on this subject.

Link to study:
[1] Effect of Dietary Sugar Intake on Biomarkers of Subclinical Inflammation
Does high fructose corn syrup contribute more to inflammation than other dietary sugars?NutritionMeta-analysis2
Answer:
No.

There was no significant glycemic impact of artificial sweeteners on average. That said, there was some variance between subjects' age, weight and whether or not they had diabetes.

Other Details:
Aspartame, saccharin, steviosides, and sucralose were all included in the examinations.

29 randomized controlled trials and 741 participants were included in this meta-analysis.

Link to study:
Review Article | Published: 15 May 2018 Carbohydrates, glycemic index and diabetes mellitus Glycemic impact of non-nutritive sweeteners: a systematic review and meta-analysis of randomized controlled trials
Do artificial sweeteners impact blood glucose levels?NutritionMeta-analysis3
Answer:
Yes...likely anyways.

"This review's findings support the hypothesis that the fasted and fed conditions can divergently influence exercise metabolism and performance. Pre‐exercise feeding bolsters prolonged aerobic performance, while seminal evidence highlights potential beneficial metabolic adaptations that fasted exercise may induce in peripheral tissues." [1]

Other Details:
The authors of the study believe more research is needed to draw any complete conclusions.

46 studies were included in this meta-analysis.

Link to study:
[1] Effects of fasted vs fed‐state exercise on performance and post‐exercise metabolism
Does fasted aerobic exercise offer any additional benefits?NutritionMeta-analysis3
Answer:
Yes, there sure are!

Active recovery, massage, compression clothing, immersion, contrast water, and cryotherapy were all tested against soreness (i.e., DOMS), fatigue, muscle damage, and inflammation.

Massage proved to be the most effective at minimizing soreness and fatigue.

Other Details:
All the methods listed above contributed at least a small amount to DOMS reduction.

Compression and water immersion were also found to work well against fatigue in particular.

Cold water immersion was effective in aiding recovery, however, long term exposure was found to negatively impact the rate of muscle growth.

99 studies were included in this meta-analysis.

Link to study:
Front. Physiol., 26 April 2018 | https://doi.org/10.3389/fphys.2018.00403 An Evidence-Based Approach for Choosing Post-exercise Recovery Techniques to Reduce Markers of Muscle Damage, Soreness, Fatigue, and Inflammation
Are there any effective post-exercise recovery techniques?MiscMeta-analysis4
Answer:
Yes.

Blood flow restriction with light loads was more effective at recovering strength than light weight training without blood flow restriction.

Other Details:
Heavy training was found to be superior to blood flow restriction training for regaining strength post injury. That said, you might want to start lifting heavy again as soon as it's safe.

20 studies were included in this meta-analysis.

Link to study:
Blood flow restriction training in clinical musculoskeletal rehabilitation
Is blood flow restriction training effective at regaining strength after injury?MiscMeta-analysis3
Answer:
Yes!

Subjects who got at least 9 hours of sleep by prolonged sleeping or extension (i.e., napping) reliably boosted athletic performance.

Other Details:
10 studies and 218 participants were included in this review.

Link to study:
Sleep Interventions Designed to Improve Athletic Performance and Recovery
Does getting extra sleep improve athletic performance?MiscSystematic Review3
Answer:
Yes, there are some interventions you can use to prepare for the event in question.

Other Details:
“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.” [1]

Link to study:
[1] Choking interventions in sports
Can you do anything to help prevent choking under pressure as an athlete?MiscSystematic Review3
Answer:
Possibly.

From MASS:
"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."

Other Details:
28 studies were included in this review

Link to study:
Influence of chronic stretching on muscle performance
Can static stretching help athletic performance?MiscSystematic Review3
Answer:
Yes.

Several injury prevention programs were utilized including landing biomechanics in relation to the ligaments, core and quad dominance theories. Changes in subjects' landing mechanics were successfully implemented (primarily peak knee abduction decrease), which should theoretically prevent jumping injuries, particularly those in female athletes.

Other Details:
28 studies and 466 subjects were included in this meta-analysis.

Link to study:
The Effects of Injury Prevention Programs on the Biomechanics of Landing Tasks
Can coaching proper landing mechanics prevent injury?MiscMeta-analysis3
Answer:
Yes.

Creatine was shown to improve memory in healthy adults.

Other Details:
The cognitive benefits were shown to be greater in vegetarians than omnivores (perhaps because they're lacking creatine consumption from meat in their diets like steak, salmon, etc).

It's also suggested that creatine may help stressed individuals, and perhaps those with dementia.

6 studies and 281 participants were included in this review.

Link to study:
Effects of creatine supplementation on cognitive function of healthy individuals
Can creatine supplementation improve brain function?MiscSystematic Review3
Answer:
Yes!

Other Details:
“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.” [1]

13 studies were included in this systematic review.

Link to study:
[1] The effect of resistance exercise on sleep: A systematic review of randomized controlled trials
Can lifting weights improve sleep quality?MiscSystematic Review4
Answer:
Yes, according to this study anyway.

Injury rates, even among the most injurious weight training sports, is still lower than most common team sports (e.g., soccer, football, basketball, etc).

Other Details:
Bodybuilding had .24-1 injuries per 1000 hours trained.

Strongman had 4.6-6.1 injuries per 1000 hours trained.

Highland games had 7.5 injuries per 1000 hours trained.

Power lifting and Olympic lifting scored somewhere in the middle of the pack.

"The shoulder, lower back, knee, elbow, and wrist/hand were generally the most commonly injured anatomical locations; strains, tendinitis, and sprains were the most common injury type. Very few significant differences in any of the injury outcomes were observed as a function of age, sex, competitive standard, or bodyweight class." [1]

20 studies were included in this review.

Link to study:
[1] The Epidemiology of Injuries Across the Weight-Training Sports
Are weight training sports safer than common team sports?MiscSystematic Review2
Answer:
Yes

"Various components of core stability were found to be related to lower extremity musculoskeletal injuries in healthy athletic populations. Core strength, core proprioception and neuromuscular control of the core were found to be a risk factor in the development of lower extremity injuries." [1]

Other Details:
9 articles were included in this review.

Link to study:
[1] Is core stability a risk factor for lower extremity injuries in an athletic population?
Does core stability affect the risk of lower body injuries?MiscSystematic Review4
Answer:
Yes!

Melatonin looks to be extremely effective at preventing and treating jet lag when flying through multiple time zones.

Other Details:
It's regarded as safe for occasional use.

Doses of .5-5mg were effective for the trials (the more, the "better").

It works pretty well for 2-4 time zones, and extremely well for more than 4 time zones.

Link to study:
Melatonin for the prevention and treatment of jet lag
Can melatonin supplementation help with jet lag?MiscSystematic Review4
Answer:
Yes.

Resistance training appears to be even more effective at reducing depressive symptoms than aerobic exercise.

Other Details:
It's in MASS' opinion that the analysis might overestimate the recorded effects. That said, the results were still significantly positive across the board.

33 randomized trials with 1877 participants were included in this meta-analysis and meta-regression study.

Link to study:
Association of Efficacy of Resistance Exercise Training With Depressive Symptoms
Can lifting weights help with symptoms of depression?MiscMeta-analysis3
Answer:
Yes!

Speed and running economy both increased in highly trained, competitive runners who underwent at least 4 weeks of strength training.

Other Details:
Subjects didn't experience any significant changes in other relevant performance indicators such as VO2max, blood lactate and body comp (for better or for worse).

5 studies and 93 participants were included in this meta-analysis.

Link to study:
Effects of Strength Training on Running Economy in Highly Trained Runners
Can strength training improve long distance running performance?MiscMeta-analysis4
Answer:
Yes.

Lifting weights seemed to have a significant impact on personal body image, including factors such as "body satisfaction, appearance evaluation, and social physique anxiety" [1].

Other Details:
Only 8 of the 11 studies reported these findings. It's in the authors' opinion that "several methodological limitations exist" [1] and "future high-quality studies with more rigorous testing methods and study designs are needed" [1].

11 studies were included in this review.

Link to study:
[1] A Systematic Review of the Effects of Resistance Training on Body Image
Can resistance training improve body image?MiscSystematic Review2
Answer:
Yes!

Strength training was deemed an effective means of injury prevention in a variety of sports.

Other Details:
Both overuse and acute injuries were observed.

Proprioception training was also shown to be effective.

Static stretching was not shown to be effective for injury prevention.

25 studies and 26610 participants were included in this review.

Link to study:
The effectiveness of exercise interventions to prevent sports injuries
Does strength training intervention help prevent sports injury?MiscMeta-analysis4
Answer:
No, not according to this study.

Stretching showed zero benefit with respect to injury prevention.

Other Details:
Both overuse and acute injuries were observed.

Proprioception and strength training were shown to be effective at injury prevention.

25 studies and 26610 participants were included in this review.

Link to study:
The effectiveness of exercise interventions to prevent sports injuries
Does stretching intervention help prevent sports injury?MiscMeta-analysis3