The relationship between resistance training volume and muscle hypertrophy is controversial. Some studies support a dose-response relationship (i.e., more sets results in greater muscle hypertrophy), while others support an inverted-U relationship (i.e., more sets results in greater muscle hypertrophy up to a point, after which performing more sets will either not contribute to muscle hypertrophy or even decrease it). The present study was designed to get to the bottom of this debate.
This Systematic review and meta-analysis of 7 randomized controlled trials (6 of which were included in the meta-analysis) compared the effect of different resistance training volumes on muscle hypertrophy. To be included, the studies had to be at least 6 weeks long, recruited participants ages 18–35 with at least 1 year of resistance training experience, reported direct measurements of muscle thickness and/or cross-sectional area, and compared groups that performed a different number of sets but used the same relative load (percentage of 1-repetition maximum 1RM).
Volume load (the number of sets multiplied by the number of reps multiplied by load) differed between studies, but they were comparable because sets of about 6 to 20 or more reps provide an equivalent hypertrophy stimulus as long as the sets are completed close to muscular failure (i.e., the point at which another rep cannot be performed while maintaining proper form).
Resistance training volume was divided into three categories: low volume (less than 12 sets per week per muscle group), moderate volume (12–20 sets per week per muscle group), and high volume (more than 20 sets per week per muscle group). The meta-analysis compared the effect of moderate-volume versus high-volume training on quadriceps, biceps brachii, and triceps brachii hypertrophy.
In two out of seven measurements, high volume was more effective than low volume for quadriceps hypertrophy, and one study reported a difference between high and moderate volume, favoring high volume. The meta-analysis found no difference between moderate and high volume for quadriceps hypertrophy.
In two out of five studies, high volume was better than low volume for biceps brachii hypertrophy, and one study reported a difference between high and moderate volume, favoring high volume. The meta-analysis found no difference between moderate and high volume for biceps brachii hypertrophy.
In two out of four studies, high volume was better than moderate volume for triceps brachii hypertrophy, and one study reported a difference between high and low volume, favoring high training volume. The meta-analysis indicated a medium increase in triceps brachii hypertrophy with high volume, compared to moderate volume.
Quadriceps hypertrophy measurements were not consistent across studies. Some studies measured the front of the thigh, while others measured the vastus lateralis or the rectus femoris. Additionally, energy intake was not reported in most of the analyzed studies, which is an important factor for eliciting muscle hypertrophy.
The big picture
The results of this study support an inverted-U relationship between resistance training volume and biceps brachii and quadriceps hypertrophy (i.e., 20 or more sets and 12–20 sets per week produced similar results) as well as a dose-response relationship between resistance training volume and triceps brachii hypertrophy (i.e., 20 or more sets produced better results than 12–20 sets). So, is it as simple as that? To maximize biceps and quadriceps hypertrophy, you should perform 12–20 sets per week, and to maximize triceps hypertrophy, you should perform at least 20 sets per week? Not quite.
There are a few factors to consider when interpreting the results. First, the results are specific to the number of “hard sets,” or sets close to (i.e., within 2 reps of) muscular failure, performed per week. Additionally, the rest interval between sets was typically 90–120 seconds. Therefore, the results may not be generalizable to training programs that have participants stop their sets further away from muscular failure or take longer rest intervals between sets.
Second, multi-joint exercise sets were counted toward triceps and biceps training volume. That means 1 set of lat pulldown or barbell bent-over row and 1 set of biceps curl both counted as 1 set of biceps training volume. Similarly, 1 set of barbell bench press or barbell military press and 1 set of triceps extension both counted as 1 set of triceps training volume.
The study suggests that high-volume training was better than moderate-volume training for triceps hypertrophy, but this does not mean that 20 or more sets of single-joint exercises (in which the triceps is the prime mover, as opposed to a supporting muscle or stabilizer like in multi-joint exercises) were better than 12–20 sets. Instead, this result means that 20 or more sets of some combination of single-joint and multi-joint exercises were better than 12–20 sets of some combination of single-joint and multi-joint exercises. The use of the term “some combination” is intentional here because the amount of volume from single-joint and multi-joint exercises varied between studies. For example, one study had participants perform 32 sets per week for biceps and 32 sets per week for triceps, with 16 sets coming from multi-joint exercises and 16 sets coming from single-joint exercises. In comparison, another study had the participants perform 30 sets per week for biceps and 30 sets per week for triceps, and only multi-joint exercises were performed.
Evidence suggests that single-joint exercises are more effective than multi-joint exercises for triceps hypertrophy, and single-joint and multi-joint exercises affect different heads of the triceps, so a combination of single-joint and multi-joint exercises may be the best recipe for maximizing triceps hypertrophy.
Because multi-joint exercises are less effective than single-joint exercises for promoting triceps hypertrophy, a higher volume of multi-joint exercises would be needed to achieve a given amount of hypertrophy.
In the 4 studies included in the meta-analysis for triceps hypertrophy, 3 reported that high volume tended to produce better results than moderate volume. Of these 3 studies, one had participants perform multi-joint exercises for 100% of their assigned volume, one had participants perform multi-joint exercises for 66% of their volume, and the third had participants perform multi-joint exercises for 50% of their volume. In the fourth study, which found no difference between groups, both groups performed 4 sets of a single-joint exercise per week and either 14 or 24 sets of multi-joint exercises.
Altogether, it’s unlikely that there is a true dose-response relationship between training volume and triceps hypertrophy. It only appears that way because the studies included in this meta-analysis had the participants perform multi-joint exercises for most of their triceps training volume, which, again, are less effective than single-joint exercises for triceps hypertrophy. If only single-joint exercises were performed, it’s probable that a moderate volume would be just as good as a high volume for triceps hypertrophy. In other words, there would be an inverted-U relationship between resistance training volume and triceps hypertrophy, just like there was for the biceps and quadriceps.
Third, training frequency varied from one to three times per week between studies. Although the meta-analyses reported that there was no difference between high and moderate volumes for biceps and quadriceps hypertrophy, there were individual studies that reported significantly greater hypertrophy in the high-volume group. These studies could just be outliers, but that doesn’t seem to be the case, as there is a plausible explanation.
In the two studies that reported greater biceps hypertrophy with high-volume training, both had the participants train the biceps three times per week. Also, one of the two studies that reported greater quadriceps hypertrophy with high-volume training had the participants train the quadriceps three times per week. These findings suggest that high-volume training may only be effective when combined with a high training frequency.
In the other study that reported greater quadriceps hypertrophy with high-volume training, the participants trained the quadriceps twice per week, and the group that performed 32 sets per week experienced greater hypertrophy than the group that performed 16 sets per week. This finding may seem to contradict the above, but there’s another plausible explanation for this discrepancy related to the participants’ baseline training volume.
The participants in the high-volume group performed 19 sets per week for the quadriceps at baseline, so weekly training volume increased by a factor of 1.7 during the study. In contrast, the moderate-volume group performed 21 sets per week for the quadriceps at baseline, so weekly training volume decreased by 5 sets during the study. Considering the pivotal role of training volume in eliciting muscle hypertrophy, the increase in training volume from baseline in the high-volume group may be responsible for the greater muscle hypertrophy observed.
In support of this theory, a 2020 study had participants increase their quadriceps training volume by 20% from baseline (individualized volume) in one leg, and in the other leg, they performed 22 sets per week (non-individualized training volume). It was found that quadriceps hypertrophy was greater in the individualized volume condition. Additionally, a 2017 study had participants increase their training volume by 20% from baseline, which resulted in an increase in muscle cross-sectional area of 7.5–7.8% from baseline.
Collectively, the results of the present study suggest that the optimum training volume for quadriceps, biceps, and triceps hypertrophy is probably somewhere between 12–20 sets per week divided evenly between two sessions. However, a higher training volume may provide additional benefits if training frequency is also increased to allow for a more optimal distribution of training volume throughout the week. In addition, the prescription of training volume needs to be individualized to maximize training adaptations. If your progress has stalled and you’re recovering well from your training, consider increasing training volume by 20%, rather than doubling your training volume overnight, which could lead to an impaired adaptive response to training and a reduction in performance, known as nonfunctional overreaching.
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