Resistance Training Volume Enhances Muscle Hypertrophy
STUDY AUTHORS: Schoenfeld BJ, Contreras B, Krieger J, Grgic J, Delcastillo K, Belliard R, Alto A.
STUDY SPOTLIGHT BY: Cody Haun, PhD, MA, CSCS
PURPOSE: The purpose of this study was to evaluate muscular adaptations between low-, moderate-, and high-volume resistance training (RT) protocols in resistance-trained men.
DESIGN: Thirty-four healthy resistance-trained men were randomly assigned to 1 of 3 experimental groups: a low-volume group (1SET) performing 1 set per exercise per training session (n = 11); a moderate-volume group (3SET) performing 3 sets per exercise per training session (n = 12); or a high-volume group (5SET) performing 5 sets per exercise per training session (n = 11). Training for all routines consisted of three weekly sessions performed on non-consecutive days for 8 weeks. Muscular strength was evaluated with 1 repetition maximum (RM) testing for the squat and bench press. Upper-body muscle endurance was evaluated using 50% of subjects bench press 1RM performed to momentary failure. Muscle hypertrophy was evaluated using B-mode ultrasonography for the elbow flexors, elbow extensors, mid-thigh and lateral thigh.
RESULTS: Results showed significant pre-to-post intervention increases in strength and endurance in all groups, with no significant between-group differences. Alternatively, while all groups increased muscle size in most of the measured sites from pre-to-post intervention, significant increases favoring the higher volume conditions were seen for the elbow flexors, mid-thigh, and lateral thigh.
AUTHOR’S CONCLUSIONS: Marked increases in strength and endurance can be attained by resistance-trained individuals with just three, 13-minute weekly sessions over an 8-week period, and these gains are similar to that achieved with a substantially greater time commitment. Alternatively, muscle hypertrophy follows a dose-response relationship, with increasingly greater gains achieved with higher training volumes.
Schoenfeld et al. published a compelling meta-analysis in 2017 which included data derived from 15 studies in the analysis and suggested that higher weekly volumes of training (e.g., total reps * weight for a given exercise over the course of a week) resulted in greater muscle hypertrophy (i.e., muscle growth), up to a point yet to be identified in the literature. More specifically, Schoenfeld et al. reported almost double the muscle growth when greater than 10 sets were completed for a given muscle over the course of a week compared to less than or equal to 5 sets per week. Hence, a relatively proportional dose-response relationship between training volume and muscle hypertrophy seemed apparent up to a point yet to be identified in various demographics (e.g., young, old, male, female, etc.).
To this end, Schoenfeld et al. recently completed the study spotlighted above in way of further clarifying the relationship between RT volume and hypertrophy. Having coordinated multiple training studies, I’d first like to complement the authors for their work and want to direct your attention to the fact that these studies are quite difficult to complete, but are very important for our understanding of adaptations to RT. With this in mind, few RT studies exceed ~12 weeks in duration. We need more longer-term, longitudinal studies involving collection of biological samples (e.g., blood, muscle) to better understand adaptive responses to RT and where “upper limits” of dosing truly lie. Until then, we must try and glean from shorter-duration studies like this one from Schoenfeld et al., which lasted only 8 weeks. On a positive note, this is around how long a “mesocycle” or typical “training phase” will last, so at least the results can be interpreted in that light. Also, Schoenfeld et al. utilized trained subjects in the study, noting that subjects self-reported RT ages of greater than or equal to 1 year at a minimum RT frequency of three times per week. Therefore, if you’re a young man reading this who falls into this category, these results most likely apply to you.
Subjects self-reported ~4 years of training experience and could squat ~1.5 x bodyweight prior to the study (e.g., ~80 kg body mass and ~120 kg back squat 1RM) so I’m confident these guys were fairly deemed “resistance-trained”. The following lifts were included in the study, and I’ve also provided a table that (in my view) reflects which muscles were primarily emphasized by the exercises employed in the study.
Importantly, ultrasound measurements of muscle thickness were only completed on the biceps, triceps, rectus femoris, and vastus lateralis so it’s unclear how the pecs and lats responded to the training. However, as demonstrated in the percent change figure above, muscles analyzed hypertrophied the most in the 5 set group. Interestingly, the previous evidence indicating more hypertrophy occurs with more volume (to a point) held true in this study as well. I’m curious how well the lats and pectoral muscles responded, but I suspect the same trend held for those muscles as well. The implications of this study are quite informative! Indeed, per the suggestion of the title, this evidence continues to support the idea that greater training volumes are necessary to maximize hypertrophy.
Considering the above, these data indicate that 45 sets per week resulted in greater hypertrophy of the quadriceps than 27 or 9 in the 3SET and 1SET groups. I think it’s important to note that three different movements were used to emphasize the quadricep musculature and this could have contributed to the fact that such high training volumes were sustainable and beneficial in this study, compared to a single exercise being employed with dosage increasing throughout the intervention. Since loading was likely significantly lighter for leg extensions than leg press or squats, this should be considered before one starts doing over 40 sets of squats per week attempting to replicate these results. That is, different exercises result in different levels of stress (both locally and systemically) and simply using a single multi-joint movement to approach these volumes should be considered with caution. A practical strategy for attempting to train at similarly high volumes to elicit maximal hypertrophic responses is to include a mix of both multi-joint and single-joint exercises with priority given to full range of motion multi-joint movements preceding the single-joint work in the general construction of training sessions.
I’m also curious if the same percent change response would have been observed in the biceps and triceps had they been trained to the same extent as the quadriceps. Based on decomposing the training program as I have above, it seems the biceps and triceps were trained for 15 sets less per week in the 5SET group compared to the quads (i.e., 30 vs 45). Since the biceps and triceps were only trained with 30 sets per week, and hypertrophied about 50 % less than the relative amount the quads did (i.e., ~3 % increases observed in the bis and tris vs ~6 % observed in the quads), it seems plausible the bis and tris would have grown in a relatively similar manner had they been trained to the same extent. Of all of the muscles measured, the tris grew the least on average (across groups). This might indicate the triceps would be better trained at a different frequency for hypertrophy, but it could also be due to a milieu of other factors this study wasn’t aimed at addressing (future research can further elucidate how different muscles specifically respond to various training doses for realizing maximal hypertrophy). Another cool finding from the study was that the 1SET group increased strength to the same extent as the 5SET group. It only took the 1SET group ~15 minutes per training session. Although the training protocol wasn’t designed for improving maximal strength specifically (i.e., 8-12 reps per set), it is intriguing that improvements in strength were made to roughly the same extent in the group of subjects spending less than an hour training per week. This can be a persuasive case to any clients, friends, or family members you might have that don’t like spending too much time at the gym. Improvements (however small) can be made with only about 15-20 minutes of hard work in the gym each session (at least in the short-term, although over time the principle of overload necessitates an increase in training load for continued improvement). This also speaks to the various aims of training and how phases can be designed to emphasize and deemphasize certain fitness attributes without worrying too much about doing a ton of damage to another so long as maintenance stimuli and overloading stimuli are structured correctly (e.g., retaining loads, heavy and light days, etc.).
With that said, it does seem the “upper limit” of dosing training volume for eliciting maximal muscle growth responses is yet to be determined and this research continues to support the notion that greater volumes result in greater hypertrophy. Future research will hopefully uncover upper limits in various demographics and help us better dose training while better identifying how programming can be fine-tuned and individualized on a daily and weekly basis. Until then,increasing dosesup to a point where various indications of when it might be time to deload occur seems like quite the viable strategy to maximize hypertrophy in the short-term.
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Cody Haun, PhD, MA, CSCS
-APLYFT Science Consultant