A popular theory among fitness professionals is that taking short rest periods between sets maximizes muscular growth. The theory is primarily based on the hormone hypothesis, whereby limiting inter-set rest promotes greater elevations in post-exercise growth hormone, IFG-1 and testosteron...
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May 29, 2016
Training frequency is one of the most hotly debated topics in the field of resistance training. While traditionally the term frequency has been associated with how many days a week you work out, a potentially more important variable is the number of times a given muscle group is trained per week.
The internet is littered with varying opinions as to optimal training frequency for maximizing muscle hypertrophy. Some preach the typical bodybuilding “bro-split” which involves training each muscle group once a week with high volumes per session, whereas others propose training each muscle as many as 6 days a week with lower per-session volumes is the best way to get jacked. Problem is, all these opinions are largely anecdotal with limited scientific support. Seems hard to believe, but there hasn’t been a whole lot of research on the topic, and the studies that have been carried out have employed a variety of methodological designs that makes it difficult to sort out a conclusion at face value.
In an attempt to achieve better clarity on the effects of frequency on muscle growth, I recently collaborated on a meta-analysis with colleagues James Krieger and Dan Ogborn. In case you’re not aware, a meta-analysis pools data from all studies on a given subject to provide greater statistical power and thus enhance the ability to draw practical inferences.
Here’s the lowdown:
What We Did
A literature search was conducted to locate all studies that directly compared measures of hypertrophy for different weekly lifting frequencies using traditional resistance training programs. Only human studies with healthy subjects were considered, and study duration had to last a minimum of four weeks.
A total of 10 studies were identified that met inclusion criteria. 7 of the studies, comprising a total of 200 subjects, investigated muscle group frequency while the other 3 studies assessed training session frequency when the number of weekly times working a muscle group was matched.
What We Found
We first looked at the effects of frequency as a binary predictor. Simply stated, this means that the higher frequency condition in a study was compared to the lower frequency condition, irrespective of how many days a week the muscle group was trained. Thus, a 2 day-a-week vs 1 day-a-week was treated the same as a 3 day-a-week vs 1 day-a-week. In this model, there was a clear benefit for higher frequency training of a muscle group. The effect size – a measure of the meaningfulness of results – was 48% greater for the higher frequency conditions (0.49 vs 0.30, respectively), translating into an average hypertrophy increase of 6.8% versus 3.7% for higher vs lower frequencies, respectively. Moreover, as shown in the accompanying chart, every study on the topic showed a benefit to training with higher frequencies.
Due to an insufficient number of studies looking at training 1, 2, or 3 days per week, we were unable to produce reliable estimates on the hypertrophic effects of specific lifting frequencies. Similarly, with only 3 studies looking at training session frequency when groups were matched for frequency of training per muscle group, data was insufficient to produce reliable estimates for effects on hypertrophy.
What are the Practical Implications
The primary take-away from the meta-analysis is that there appears to be a pretty clear benefit to training muscle groups with higher weekly frequencies. At the very least, the study shows that training a minimum of 2 days a week is needed to maximize muscle growth. Unfortunately there simply aren’t enough studies to make more concrete determinations as to the precise number of times that a muscle should be trained each week for optimal growth. Nevertheless, training a muscle just once a week was shown to promote substantial muscle growth. So the claims made by some that the typical bro-split only works for juiced-up bodybuilders are patently false.
It’s important to realize that research studies are relatively short-term, usually lasting 6 to 12 weeks. Problem is, you can’t necessarily extrapolate that results found would continue over time. This is particularly true of a variable such as frequency, as high training frequencies may ultimately lead to an overtrained state and thus have a negative impact on muscle development. Given such a possibility, it may be prudent to periodize training frequency, varying the number of times a muscle is trained each week in a systematic fashion. It also indicates a potential benefit to instituting regular deload periods, where a week of reduced frequency, volume, and/or intensity is strategically integrated into your program every month or so to facilitate recuperation and regeneration.
Importantly, remember that research reports the average responses, but there are generally large inter-individual differences in results. Some may respond best to higher frequencies while others might do better with lower frequencies. Use research to guide your programming, then experiment to see what works best for you.
April 6, 2016
If you follow my work you’ll undoubtedly know that our lab has carried out a number of studies seeking to determine the effects of training in different repetition ranges on muscle strength and growth. The overall findings from these studies showed similar increases in hypertrophy between both heavy and moderate rep ranges, as well as moderate and high rep ranges.
However, the choice of rep ranges is not necessarily an either-or proposition; you can in fact combine strategies to potentially achieve greater hypertrophic benefits. Daily undulating periodization (DUP) routines are specifically designed for this purpose. However, no study to date had compared a varied rep approach to traditional constant-rep training using site-specific measures of muscle growth.
Our study, just published in the International Journal of Sports Medicine, set out to investigate if muscular adaptations would differ between DUP-style routine and a traditional hypertrophy-style protocol. Here’s the scoop.
What We Did
Nineteen young men with over four years average resistance-training experience were randomly assigned to 1 of 2 experimental groups that trained 3 days per week: a constant-rep protocol (CONSTANT) that trained using a standard bodybuilding rep range of 8-12 RM per set, or a DUP-style varied-rep protocol (VARIED) that trained with 2-4 RM per set on Day 1, 8-12 RM per set on Day 2, and 20-30 RM on Day 3. All subjects performed a total-body routine consisting of the following seven exercises per session: flat barbell press, barbell military press, wide grip lat pulldown, seated cable row, barbell back squat, machine leg press, and machine knee extension. We tested subjects for changes in hypertrophy of the arm flexors, elbow flexors and quads, as well as maximal strength in the squat and bench press, and upper body muscle endurance. Training was carried out over an 8-week period, with testing done pre- and post-study.
What We Found
Both groups significantly increased markers of muscle strength, muscle thickness, and local muscular endurance. No statistically significant differences were found between conditions in any of the outcomes studied. Sounds like it really doesn’t matter which option you choose, right?
Well, not so fast…
It’s important to understand that the term “statistically significant” simply refers to the probability of results being due to chance at a predetermined level of 5%. This binary method of determining probability has been widely criticized by those in the know about statistics, who proclaim that practical conclusions cannot be drawn merely on the basis of whether a p-value passes a specific threshold. Rather, probability exists on a continuum, and in this regard the p-values (a measure of probability) in our study favored the VARIED condition in several outcome measures. Moreover, magnitude-based statistics (i.e. effect sizes) indicated a benefit to the VARIED condition for upper body hypertrophy, strength, and muscular endurance; no effect size differences were noted for lower body outcomes.
What are the Practical Implications
The study showed a potential benefit – albeit small – to varying repetitions across a spectrum of ranges for increasing upper body muscle strength and hypertrophy. Whether the differences between the varied versus constant rep approach seen in our study would amount to practically meaningful improvements is specific to the individual. For the average gym-goer it probably wouldn’t be of much consequence; alternatively, to a bodybuilder or competitive athlete it very well may. It’s not clear why these findings did not translate into similar differences in lower body muscular adaptions, but based on our findings either approach would seem to be an equally viable choice for leg training.
It’s important to note that this was a relatively short-term study, lasting a total of 8 weeks. When factoring in missed sessions, this means subjects in VARIED trained in each loading zone for a total of only 7-8 sessions over the course of the study period. If the differences in upper body outcomes favoring VARIED would persist over time – highly speculative but certainly possible – the magnitude of results could widen and thus be potentially meaningful for a wide array of fitness enthusiasts.
Another important point is that volume load was consistently lower across all conditions (pushing exercises, pulling exercises, leg exercises, and total volume of all exercises) in VARIED as compared to CONSTANT. This indicates that training in a varied fashion provides comparable or better results with less volume load than training at a constant 8-12 RM repetition range. It also suggests that if volume load were equated between conditions, there might have been even better results for the varied approach.
In sum, our study shows that both varied and constant loading schemes are viable strategies to increase strength and hypertrophy in resistance-trained men. The data suggest a potential modest benefit to varying loading ranges over time, at least for maximizing upper body muscular adaptations. Importantly, findings clearly indicate that contrary to what many believe, training in the “hypertrophy zone” (6-12 RM) is not superior for building muscle. When considering the practical implications of the findings, remember that exercise prescription is always a function of the needs/abilities/goals of the individual.
February 12, 2016
Wanted to keep you updated on all that is going on at the moment. So much to share!
First and foremost, I’m excited to announce that I have two soon-to-be-released books. One is a consumer book, called Strong and Sculpted, that’s targeted to women who want to optimize muscle development. The book details a complete periodized program to achieve this goal, combining the latest scientific evidence with time-tested experience from the field. The other is a textbook called, Science and Development of Muscle Hypertrophy. This book is the culmination of my professional life to date. It is the first text solely devoted to exploring the science of maximizing muscle growth through regimented exercise. I cover the molecular basis of hypertrophy, the mechanisms, the practical application of resistance training variables, and the different periodization models that can be used to optimize results. There are chapters on the effects of aerobic exercise and nutrition, as well. No stone is left unturned. I couldn’t be more proud of this effort. Both books are available for pre-order by clicking on the highlighted links.
Here’s a vid of the cross cable reverse fly exercise. It’s one of my favorite exercises for targeting the posterior delt. Notice the control throughout both the eccentric and concentric actions, making sure to keep constant tension on the target muscle.
I have numerous speaking engagements scheduled for this year that will take me around the globe. I’m particularly excited about a couple of upcoming events where I’ll share the stage with my esteemed colleagues Alan Aragon, Bret Contreras, and James Krieger. We’ll be speaking at the inaugural Personal Training Collective Annual Conference to be held at the University of Bath in England on April 23 and 24. We next will be speaking in Sydney, Australia at Bropocalypse 2016 taking place on June 11th and 12th. These events are sure to sell out so get your tix early! My travels will also include engagements in Denmark, Norway, Brazil, and New Orleans, with others currently in discussion. I’ll keep you all posted over the coming weeks.
I recently co-authored a paper with Bret Contreras on the “mind-muscle connection” that was published in the current issue of the NSCA Strength and Conditioning Journal. In the paper we lay out evidence that suggests a potential benefit to the approach for maximizing muscle growth. It’s a really interesting topic that needs more research; as such, I have a study planned for later this year that will hopefully shed more light on its efficacy. You can read the full text of the paper, as well as most of my other published works, on my Researchgate page
August 13, 2014
There is compelling evidence that the onset of fatigue during resistance training results in an increase in motor unit activation, whereby the strength-oriented type II fibers are progressively recruited to sustain muscular contractions. Some have taken this to mean that any load, regardless of how light, will ultimately lead to full fiber recruitment provided that training is carried out to muscle failure (i.e. the point where you are unable to complete an additional rep with proper form).
Recently, my lab sought to test this hypothesis. Here is an overview of the study and its practical implications. The study, titled, Muscle activation during low- versus high-load resistance training in well-trained men, was just published ahead-of-print in the European Journal of Applied Physiology.
The purpose of the study was to compare muscle activation in the leg press at 30% and 75% 1RM when sets are carried out to muscular failure. Ten college-aged men were recruited for participation. Subjects were all experienced in resistance training, including regular performance of lower body exercise.
A within-subject design was employed where each participant performed both 30% and 75% 1RM conditions. Testing was carried out over two sessions. Subjects were initially tested to determine their 1RM in the leg press. They then returned to the lab at least 48-hours later for muscle activation testing of the quads (rectus femoris, vastus lateralis, and vastus medialis) and the hamstrings (biceps femoris) during heavy- vs. light-load training. The order of performance was counterbalanced whereby Subject 1 performed the high-load condition first, Subject 2 performed the low-load condition first, etc. In this way, we ensured that order of performance did not confound results. Fifteen minutes rest was provided between trials to ensure that previous fatigue was not a factor. We verbally encouraged subjects to perform each set to the point where they could physically no longer continue training with proper form.
Both mean and peak muscle activation was markedly and significantly greater during the heavy- compared to light-load condition (by 57% and 29%, respectively). Importantly, not a single subject displayed equal or greater activation during low-load training. These findings strongly suggest that training at 30% 1RM in a compound lower-body exercise is insufficient to recruit the entire motor unit pool for the target musculature.
It has been well-established that training to muscle failure causes an increase in motor unit recruitment. This outcome was in fact confirmed in our study, as EMG amplitude increased in both the high- and low-load conditions over the course of each set. However, the magnitude of these increases were substantially lower during light- versus heavy-loading. The take home message here (in conjunction with a recent study on the topic using single-joint lower body exercise) indicates that a minimum threshold exists to achieve activation of the full spectrum of fibers and that 30% 1RM is below this threshold. Thus, it can be inferred that some of the highest threshold motor units — those associated with the type IIx fibers — were not recruited during the low-load condition.
From an applied standpoint, it might seem that these findings show training at very low-loads is useless. After all, why would you train with a load that does not generate complete fiber recruitment, right?
Not so fast.
Understand that there are two aspects to maximizing muscle development: recruiting a fiber and then keeping it stimulated for a sufficient period of time (i.e. time under load). While the loading strategy used in the light-weight condition here (i.e. 30% 1RM) did not bring about full muscle activation, it did maintain tension in the lower-threshold motor units for an extended time period. This could be particularly important in optimizing development of the type I fibers that are highly fatigue-resistant. This lends credence to the hypothesis that training throughout the full spectrum of rep ranges is the best strategy for maximal muscle hypertrophy. I have a longitudinal training study currently in review that seems to support this hypothesis. More on that in the near future.
An interesting secondary finding of the study was that the hamstrings displayed only minimal activation during the leg press — much less than that seen in the quads. This refutes the claims by some fitness pros that single-joint exercise is unnecessary provided you perform compound lower body exercises. Our results clearly indicate that movements such as the leg curl, stiff-leg deadlift, and good morning are important components of a well-rounded resistance training program to ensure proper symmetry between the quads and hamstrings.
A limitation of the study is that we only assessed a single set at each condition. Thus, it is not clear whether accumulated fatigue from performing multiple light-load sets would ultimately bring about complete recruitment. This requires further study. But even if this turns out to be the case — which is far from a certainty — it would mean that you’d need to perform a lot of additional volume just to achieve similar levels of activation; at the very least, an inefficient training strategy.
I am in the process of finishing a follow-up bench press study looking at 80% vs. 50% 1RM in an attempt to determine the approximate minimum threshold necessary for complete muscle activation. This will provide important info to those who are unable to lift heavier weights due to medical conditions or other issues. Realize, though, that muscle activation (and hypertrophy for that matter) do not necessarily translate into optimal strength gains. My recent study showed that even moderate load training (~10 RM) is inferior to very heavy lifting (~3 RM) if absolute strength is the goal. I discussed that study in-depth in this blog post
On a side note, I’ll be discussing the ramifications of this study and others currently in progress at my upcoming seminar in Montreal next month. Hope to see you there!
Cook SB, Murphy BG, Labarbera KE. Neuromuscular function after a bout of low-load blood flow-restricted exercise. Med Sci Sports Exerc. 2013 Jan;45(1):67-74.
Schoenfeld BJ, Contreras B, Willardson JM, Fontana F, Tiryaki-Sonmez G. Muscle activation during low- versus high-load resistance training in well-trained men. Eur J Appl Physiol. 2014 Aug 12. [Epub ahead of print]
Schoenfeld BJ, Ratamess NA, Peterson MD, Contreras B, Tiryaki-Sonmez G, Alvar BA. Effects of different volume-equated resistance training loading strategies on muscular adaptations in well-trained men. J Strength Cond Res. 2014 Apr 7. [Epub ahead of print]
July 6, 2014
In this post I want to delve into the specifics of a study I recently published in the Journal of Strength and Conditioning Research that investigated muscle activation in two popular hamstrings exercises: the stiff leg deadlift and the lying leg curl. While other studies have evaluated differences between these exercises in activation of the medial hamstrings (semitendinosus and semimembranosus) versus the lateral hamstrings (biceps femoris), our study is unique in that we also looked at activity in the upper and lower aspects of the individual muscles.
My interest in undertaking this work revolves around an emerging body of research showing that, contrary to popular belief, muscle fibers do not necessarily span from origin to insertion. Rather, many muscles are compartmentalized so that fibers terminate intrafascicularly (within the fascicle) with each subdivision innervated by its own nerve branch. This structure provides a mechanism by which different exercises can conceivably target different portions of a given muscle. It just so happens that several studies have shown that the hamstrings muscles are in fact partitioned in a manner that would potentially allow for such regional-specific activation. I thus decided to test this hyptothesis in the lab under controlled conditions.
What We Did
Ten young men were recruited to participate in the study. All of the subjects were experienced with resistance training, defined as lifting at least 3 times per week for a year or more. We employed a counter-balanced design where each subject performed both the stiff-leg deadlift and the leg curl. This design provides a high-degree of statistical power, thereby improving the possibility of detecting a significant difference if one in fact does exist. Testing took place over two sessions. In the first session we tested subject’s 8RM on both exercises. The second session involved assessing activation during performance of the movements at the subject’s 8RM.
Muscle activation was determined by a technique called electromyography (EMG). Electrodes were placed on the upper and lower aspects of the subject’s medial and lateral hamstrings; care was taken in placement to make sure that cross-talk between muscles did not confound results. The subjects then performed one of the exercises followed by a lengthy rest period and then performed the other exercise. The exercises were counterbalanced so that Subject 1 performed the leg curl first, Subject 2 performed the stiff-leg deadlift first, etc. This ensured that the order of performance did not confound results. All sets were performed at the subject’s 8RM to muscular failure.
What We Found
Activation of the upper hamstrings was similar between exercises. Interestingly, however, activation of the lower hamstrings, both medially and laterally, was significantly greater in the lying leg curl. The differences in activation of the lower hamstrings was stark, with the leg curl showing greater lower lateral hamstrings activity of ~170% and lower medial hamstrings activity of ~65% compared to the stiff-leg deadlift. The data for the lateral hamstrings was not unexpected; the short head of the biceps femoris does not cross the hip joint, so a knee-dominant exercise such as the leg curl would necessarily be the only way to directly target this muscle. However, the data for the medial hamstrings was somewhat surprising since both the semitendinosus and semimembranosus are biarticular muscles. Results suggest that the partitioning of these muscles may allow for greater regional-specific activation in their lower aspect.
The findings suggest that performing both a hip-dominant hamstrings exercise (such as the stiff-leg deadlift) and a knee-dominant exercise (such as the leg curl) are beneficial to maximize activation of the muscle complex. Given that muscle hypertrophy is predicated on recruiting as many motor units as possible in the target muscles and achieving high firing rates in these motor units for a sufficient length of time to fully stimulate the fibers, it stands to reason that greater activation achieved should lead to greater regional-specific muscle growth. Several recent studies have in fact shown this to be the case, with non-uniform hypertrophy correlating to the region of greatest muscle activation. However, the evidence to date remains correlational and more research is needed to draw cause-effect conclusions. In the meantime, the present study provides interesting insight into how different exercises elicit different responses in a given muscle and lends support to the potential benefits of varying exercise selection to optimize muscle development.
Schoenfeld BJ, Contreras B, Tiryaki-Sonmez G, Wilson JM, Kolber MJ, Peterson MD. Regional Differences in Muscle Activation During Hamstrings Exercise. J Strength Cond Res. 2014 Jun 24. [Epub ahead of print]