The Science of How Many Sets Optimize Muscle Hypertrophy

how many sets for hypertrophy

Within the fitness world, there seem to be diverse opinions on how many sets a person should perform to build muscle optimally.

On one end of the spectrum, some believe a low number of sets is sufficient, with some even proposing 1 set of repetitions to failure per exercise is all you need to build muscle.

On the other end of the spectrum, others suggest that so long as you can successfully recover from it, more sets mean more stimulus, thus the higher number of sets you can perform the better for muscle growth.

However, what does scientific research say?

Before exploring the research, it’s useful to get some definitions and technical points out the way.

Definition of a Set

What Repetition Ranges Are We Talking About?

In this article, a set is defined as a bout of repetitions between 8 and 12, performed 3 or fewer repetitions from the point of failure. This is what pretty much all the research we’ll explore in this video used as a set. 

However, technically, we could perhaps extend this definition to repetitions between 5 and 35, performed 3 or fewer repetitions from the point of failure. This is because the research indicates repetitions between 5 and 35 (when performed 3 or fewer repetitions from failure) are similarly effective for building muscle, with all other training variables equal.

However, there is a reason why it might not be sensible to include reps as higher than 20 in this definition. Higher repetitions (20+), performed 3 or fewer repetitions from failure, seem to potentially be meaningfully more fatiguing and require longer recovery durations than lower repetitions (<20). 

Therefore, one could suggest that the recommendations in this video may not translate to sets of 20+ reps, as they are more fatiguing than <20 rep sets.

This could very well be true, but there does exist a counter to this argument. Higher repetitions are likely more fatiguing and require longer recovery periods only once you first expose yourself to them. As you continue training with high repetitions, your body likely produces a range of protective adaptations that mean you experience less fatigue and faster recovery (this is something called the repeated bout effect). Thus, after a while, you may have the capacity to recovery similarly between a set of 20+ reps and a set of <20 reps, meaning the conclusions in this video eventually do apply to 20+ rep sets.

Overall, given there is no direct data that can confirm or deny this, it’s difficult to say. Nevertheless, although the majority of the research explored in this article used sets of 8-12 repetitions, we can probably assume that the recommendations from the research should extend to sets of 5-20 repetitions at the very least.

We’re Exploring Weekly Sets, and What This Means

In this article, we’ll actually be exploring how many weekly sets you may want to be performing for each muscle group. 

Any exercise that involves a muscle group as a prime mover will count towards that muscles group’s weekly sets.

For example, in a compound exercise like the bench press, the chest, triceps, and deltoid muscles are prime movers. Thus, one set on the bench press will count towards 1 set for the chest, 1 set for the triceps, and 1 set for the deltoids. 

Also, any isolation exercises that target a specific muscle group will of course count towards that muscle group’s weekly sets. For instance, 1 set on the triceps skull crusher will count towards 1 set for your triceps. 

Okay, let us now explore the research on how many weekly sets you should perform per muscle group to maximize muscle hypertrophy.

More Sets = More Muscle Hypertrophy?

Kicking things off, the results from a meta-analysis by Schoenfeld et al. seem to indicate that the more sets performed for a muscle group per week, the more muscle growth. 

Based on data from 15 studies, each additional weekly set was associated with an 0.37% increase in muscle size.

Furthermore, performing 9 or more weekly sets for a muscle group produced more muscle hypertrophy than fewer than 9 weekly sets.

However, there are two important considerations with this meta-analysis.

Firstly, the majority of the studies included did not have subjects perform more than 9-12 weekly sets for a muscle group.

Secondly, the majority of the studies were also conducted on previously untrained individuals. 

As a result, probably the most accurate takeaway from this analysis is that for beginners, performing 9-12 weekly sets per muscle group is likely better than fewer. 

This is probably a solid takeaway for beginners. 9-12 weekly sets is probably an ideal amount of work for them. 

We know that beginners gain the fastest rate of muscle and strength, but they also experience the most muscle damage and longest recovery durations. Thus, performing more than 9-12 weekly sets may not be necessary for them.

What About More Than 9-12 Weekly Sets for Trained Individuals?

What about once a beginner gains a good degree of experience, and what about individuals with numerous training years of experience?

Could performing more than 9-12 weekly sets for trained individuals benefit muscle hypertrophy?

As far as I’m aware, there have been 6 studies exploring this. 3 of them essentially indicate the more sets the better, while the other 3 suggest there’s a point where further weekly sets provide no further benefit or even regression for hypertrophy.

Let us briefly examine these 6 studies in hope of finding reasons that could explain the overall mixed results. 

We’ll first examine the 3 studies that find more sets to be better.

The More Sets the More Growth?

Brigatto et al. had 27 men with an average of 3.5 years of training experience either train their muscle groups with 16, 24, or 32 weekly sets.

All groups distributed their sets over two non-consecutive days a week, and training lasted 8 weeks.

50% of the weekly sets for a muscle group were from compound exercises, with the remaining 50% coming from isolation exercises.

Also, 60-second rest intervals were used between sets in a session.

Increases in biceps, triceps, and vastus lateralis thickness were greatest for the subjects performing 32 weekly sets for their muscle groups.

Radaelli et al. had 48 men with previous calisthenics experience train their biceps with either 6, 18, or 30 weekly sets. Moreover, subjects either trained their triceps with 9, 27, or 45 weekly sets. 

All groups distributed their sets over three non-consecutive days a week, and training lasted 6 months.

For their biceps, 50% of the weekly sets were from compound exercises, while the remaining 50% was from isolation exercises.

For the triceps, 2/3 of the sets were from compound exercises, while 1/3 were from isolation exercises. 

Also, 90-120 seconds of rest was given between sets in a session.

Increases in biceps and triceps thickness favored performing the highest number of weekly sets.

Schoenfeld et al. had 34 men with an average of 4.4 years of training experience perform either 6, 18, or 30 weekly sets for their biceps and triceps. Moreover, subjects either trained their quadriceps with 9, 27, or 45 weekly sets.

All groups distributed their sets over three non-consecutive days a week, and training lasted for 8 weeks.

For the biceps and triceps, 100% of the weekly sets were from compound exercises. For the quadriceps, 2/3 of the weekly sets were from compound exercises, with the remaining 1/3 from isolation exercises.

Also, 90 seconds of rest was given between sets in a session.

Increases in biceps, triceps, rectus femoris, and vastus lateralis thickness favored performing the highest number of weekly sets. 

So, these three studies we’ve just overviewed indicate between 30-45 weekly sets for a muscle group are beneficial for muscle hypertrophy.

Let us now briefly detail the 3 other studies that oppose this, and then figure out why this could be.

More Sets Are Not Better

Heaselgrave et al. had 49 men with at least 1 year of training experience train their biceps with either 9, 18, or 27 weekly sets.

The subjects that performed 9 weekly sets performed this all in one session, while the subjects that performed 18 or 27 weekly sets distributed it over two non-consecutive days a week. Training lasted 6 weeks. 

2/3 of the weekly sets were from compound exercises, with the rest from isolation exercises.

Also, 3 minutes of rest between sets was used in a session.

Increases in biceps thickness seem to favor the group performing 18 weekly sets for the biceps, suggesting this is an optimal number of weekly sets.

Ostrowski et al. had 35 men with between 1-4 years of training experience train their triceps with either 7, 14, or 28 weekly sets.

All subjects distributed their weekly sets over two non-consecutive days per week, and training lasted 10 weeks.

70% of the weekly sets were from compound exercises, with the remaining 30% from isolation exercises.

Also, 3 minutes of rest between sets was used in a session.

Increases in triceps thickness were similar between the subjects performing 14 and 28 weekly sets, and both were greater than the subjects performing 7 weekly sets. Therefore, this data suggest 14 weekly sets is sufficient, with extra sets providing no further benefit. 

Finally, Aube et al. had 35 men with at least 3 years of training experience train their quadriceps with either 12, 18, or 24 weekly sets.

All subjects distributed their weekly sets over two non-consecutive days per week, and training lasted 8 weeks.

100% of the weekly sets were from compound exercises.

Also, 2 minutes of rest between sets was used in a session.

Increases in anterior thigh thickness at two regions were statistically similar between all three weekly set groups. Indicating that 12 weekly sets may be sufficient.

So, these three studies collectively indicate that between 12-18 weekly sets may be sufficient, or perhaps even optimal (in the case of the Heaselgrave et al. study), for building muscle.

Why the Conflicting Research?

Why might these 3 studies conflict with the other 3 studies that suggest more weekly sets result in more muscle hypertrophy?

There are three potential hypotheses I can think of.

Individual Differences

Firstly, perhaps individual differences explain the conflicting results. 

More specifically, the optimal number of weekly sets may be highly individualized. The 3 studies that found more sets to be better might have predominantly recruited subjects that respond favorably to a high number of weekly sets, while the other 3 studies may not have.

To some degree, I think part of this hypothesis is true. That is, it’s probably very likely that certain individuals respond better to a high or lower number of weekly sets for a muscle group. 

However, this might not be the only thing going on, as we’ll see with the second and third hypotheses.

Rest Interval Differences

The second hypothesis, relating to rest intervals, might actually be a very strong hypothesis that could explain the divergent results.

More precisely, the 3 studies that found more sets to be better seemed to predominantly have subjects rest 60-90 seconds between their sets in a session. Put differently, they used short rest intervals.

In contrast, the 3 studies that found 12-18 weekly sets per muscle group to be sufficient or optimal had subjects rest 2-3 minutes between sets in a session. In other words, they used long rest intervals.

The reason this is potentially significant is that the research seems to indicate using long rest intervals makes each set more effective for building muscle.

We’ve explored this in-depth in our rest interval article. However, let us briefly detail a study by Longo et al. that demonstrates this concept extremely well. 

They found that when performing 3 sets of repetitions to failure with an 80% one-rep max load on a leg press, resting for 3 minutes between sets produced greater increases in quadriceps cross-sectional area versus resting for 1 minute between sets. However, when subjects performed 4 to 5 sets of repetitions to failure with an 80% one-rep max load and used 1 minute of rest between sets, quadriceps cross-sectional area increases were similar to performing 3 sets of repetitions to failure with an 80% one-rep max load and using 3 minutes of rest between sets. 

(Data are mean ± standard deviation)

Therefore, this study nicely demonstrates that longer rest intervals make each set more effective for building muscle. If you use shorter rest intervals between sets, you have to perform more sets to receive similar growth to using longer rest intervals.

Now, it should be noted that a leg press, a compound exercise, was used in this study. This conclusion we’ve just made seems to be only relevant to compound exercises, the research on rest intervals with isolation exercises is far from clear.

Nevertheless, many compound exercises were used in the studies explored in this video, and perhaps this logic explains the results.

Given longer rest intervals make each set more effective, it perhaps makes sense that the 3 studies that used longer rest intervals found 12-18 weekly sets per muscle group to be sufficient or optimal.

Conversely, given shorter rest intervals require you to perform a higher number of sets to receive the equivalent muscle growth to using longer rest intervals, it makes sense that the three studies that used short rest intervals found that up to 30 to 45 weekly sets per muscle group provided more benefit for muscle hypertrophy.

Of course, it’s important to recognize this is only a hypothesis. However, I personally believe it’s a pretty strong hypothesis and may indeed explain the results.

Training Frequency Differences

The third hypothesis, relating to training frequency, adds a further twist to our interpretation of the evidence.

The 3 studies that found 12-18 weekly sets to be sufficient or optimal for building muscle all had subjects distribute their weekly sets for a muscle group over only 2 days a week. 

It’s possible there could exist a limit to the number of sets you can perform for a muscle group per session, meaning that the highest number of set groups in these studies, which we know performed around 24-28 weekly sets per muscle group, might have experienced more muscle growth if they distributed their weekly sets across more than two days a week.

However, does a limit to the number of sets you can perform for a muscle group each session actually exist?

One factor we might have to consider here is the one we’ve just mentioned: rest interval durations.

It’s likely that if a limit to the number of sets you can perform per session exists, it would be lower when using longer rest interval durations compared to using short rest intervals durations, because as we’ve mentioned, longer rest intervals make each set more effective.

In the three studies that found 30-45 weekly sets per muscle group produced more muscle growth, we know they used short rest intervals.

Moreover, they had subjects distribute their weekly sets over two to three days each week. In essence, this meant that the subjects performing 30-45 weekly sets per muscle group were performing 15-16 sets for a muscle group each session. 

As the subjects that did this experienced the most growth compared to others performing fewer sets, we can potentially conclude that performing 15-16 sets per muscle group each session is within any potential limit to the number of sets you can perform per session for a muscle group when using shorter rest intervals.

However, this information fails to help us understand what the limit could be when using longer rest intervals. 

Unfortunately, there are no direct studies that can help us here. But, there are two studies that may somewhat give us clues.

A study by Ogasawara et al. subjected the gastrocnemius of rats to sets of 10 electrically induced muscle contractions, using 3 minutes of rest between sets (which is a long rest interval).

They found that muscle protein synthesis progressively increased up to performing 10 sets of this per session. However, muscle protein synthesis was less when performing 20 sets per session.

As a result, this data potentially suggests that the limit the number of sets you can perform per muscle group each session when using longer rest intervals lies between 10-20 sets.

Of course, two important limitations of this study are that rats were used, and only acute muscle protein synthesis measurements, not long-term muscle growth measurements, were explored.

Another study by Damas et al., conducted on humans, provides potential further insight.

They found that when performing 12 sets for the quadriceps in one session, muscle protein synthesis increases seemed to have only been slightly greater compared to performing 8 sets for the quadriceps in one session. They used 2-minute rest intervals between sets in this study (which is probably just about what we’d call a long rest interval).

As a result, this data potentially implies, when using longer rest intervals, performing 12 or more sets per muscle group each session may not result in much further benefit, indicating this could be near or at the limit to the number of sets you can perform per muscle group each session.

Of course, a limitation is that only acute muscle protein synthesis measurements, not long-term muscle growth measurements, were assessed.

Nevertheless, returning to the 3 studies that found 12-18 weekly sets to be sufficient or optimal for building muscle, and used longer rest intervals, we know that the highest set groups in these studies, performing 24-28 weekly sets, distributed their sets across 2 days a week.

This means they performed roughly 12-14 sets for a muscle group each session, and this number is potentially at or past the potential limit indicated by the Ogasawara and Damas studies. Thus, perhaps if they distributed their weekly sets across 3 or more days a week, they would have experienced more muscle growth than the other groups performing fewer weekly sets.

Of course, it’s important to recognize this is a hypothesis based on limited data. Ultimately, future direct research would be needed to truly prove if this is correct.

Increasing the Number of Sets as a Tool for Low Responders or Plateaued Individuals

Moving on to the final section of this article, for the majority of the readers that are currently training, there’s a good chance that you probably don’t have to change your training based on the research recommendations presented.

Regardless of whether you are above, within, or below the weekly set recommendations, if you’re making progress with your current training program, there’s probably no need to change things.

On the other hand, and this is probably one of the more important sections of this article, if in the future (or now itself) you experience a plateau in muscle hypertrophy, or you’re minimally responding to your program hypertrophy-wise, you may want to modestly increase the number of sets you perform for your muscle groups.

The reason I say this is because two studies demonstrate that increasing the number of sets you perform can probably be effective for spurring on more muscle hypertrophy in plateaued or low responding individuals. 

A study by Aube et al., which is one study we’ve already overviewed in this video, demonstrates this.

As we noted, this study found in men with at least 3 years of training experience, there was no statistical difference in anterior thigh growth between performing 12, 18, or 24 weekly sets for the quadriceps.

However, after the study, the researchers did something quite interesting. 

They split the subjects, based on their results, into one of three groups: 

  • A low responder group, which contained subjects that grew the anterior thigh the least
  • A high responder group, which contained subjects that grew the anterior thigh the most
  • A moderate responder group, which contained subjets that grew the anterior thigh to an extent between the other two groups.

Remember, the subjects of this study had at least 3 years of training experience and were training before the study took place. 

Fascinatingly, it seems that those that grew their anterior thigh the most in the high responder group had increased their weekly sets by the greatest number relative to what they were doing before the study.

Specifically, they were performing an average of 6 more weekly sets for the quadriceps. For the moderate responders, they were performing an average of 4 more sets relative to what they were before the study, and for the low responders, they were only performing around 1-2 more sets than what they were doing before the study.

Therefore, this study indicates increasing the number of sets you perform can help further enhance the muscle growth you experience, and perhaps may be a useful tool to get past plateaus or aid low responders.

Now, in this study, the subjects experienced the most benefit by increasing the number of sets for a muscle group by roughly 6 per week. 

However, larger jumps than this might not actually be better. 

Scarpelli et al. illustrates this.

They recruited 16 men with at least 2 years of training experience and had them train the unilateral (one-leg) leg extension and leg press.

With one leg, each subject individually performed 20% more weekly sets for their quadriceps than what they were doing before the study. While with their other leg, all subjects performed a prescribed number of weekly sets for their quadriceps (this ended up being 22 weekly sets).

After an 8-week training duration, increases in vastus lateralis cross-sectional area were significantly greater for the leg that performed 20% more weekly sets for their quadriceps.

Put differently, a progressive increase in weekly sets (20%) seems to be beneficial for muscle growth.

Now, here’s an important point, for 8 out of 16 of the subjects, the prescribed number of weekly sets (again, 22 weekly sets) was actually more than 20% of the weekly sets they had been performing for their quadriceps prior to the study (it ranged from being 30% to 120% more weekly sets than usual for these subjects). 

Yet, results still favored the leg that was only performing 20% more weekly sets. This finding emphasizes that larger jumps (30-120%) in weekly sets are not necessarily better than more modest (20%) increases in weekly sets for muscle hypertrophy.

So, to summarize this final section of the article, if you consider yourself a low responder or you have plateaued, modestly increasing the number of weekly sets you perform for a muscle group (perhaps by 20%) may be of great benefit. 

However, although this conclusion probably applies to many people, there are likely some individuals out there who contrastingly experience greater adaptations with lower weekly set numbers.

Some Individuals Respond Best to Lower Weekly Sets

Hammarström et al. had 16 men and 18 women train the unilateral leg press and leg extension, with a 7-10 rep max load, three times per week for 12 weeks.

With one-leg, subjects trained each exercise with only one set, resulting in a total of 6 weekly sets for the quadriceps. With the other leg, they trained each exercise with three sets, resulting in a total of 18 weekly sets for the quadriceps.

Cross-sectional area of the quadriceps was measured before and after the study.

The graph below shows the individual responses for each participant, with the Y-axis showing the cross-sectional area increases for the leg that trained each exercise with 3 sets, and the X-axis showing the cross-sectional area increases for the leg that trained each exercise with 1 set.

Quite a few participants demonstrated better gains when performing 3 sets per exercise, as you’d expect based on the research provided in this video. However, there were still a few subjects that responded slightly better with performing one set per exercise. This study nicely underscores the idea that individual differences without a doubt exist.

Takeaway Points

That brings us to the end of the article, let us summarize the article into a few key takeaway points to make everything crystal clear.

  • For beginners, 9-12 weekly sets per muscle group is probably sufficient for building muscle.
  • In more trained individuals, if you use long rest intervals between sets (2 or more minutes), 12-18 weekly sets per muscle group might be sufficient. However, although very tentative at this time, performing more than this could provide more muscle growth if you distribute your weekly sets across three or more days per week.
  • If you use short rest intervals between sets (90 seconds or less), up to 30-45 weekly sets per muscle group could be beneficial for muscle hypertrophy, provided these sets are distributed across 2 or more days per week. However, this is probably not practical or sustainable for most people, so perhaps you’d simply want to opt for using longer rest intervals with fewer sets.
  • For many individuals reading this that are currently training, so long as you are making progress, you definitely do not have to change anything based on this video. However, once you hit a plateau, or if you consider yourself a low responder, you may wish to modestly increase the number of sets you perform per muscle group each week (probably by 20%), as this could be beneficial.
  • Finally, it’s worth remembering individual differences are real. Some individuals out there might actually experience better muscle hypertrophy when performing a lower number of sets per muscle group.

RECEIVE 2 INFOGRAPHICS WEEKLY SUMMARIZING VARIOUS HYPERTROPHY AND STRENGTH RELATED RESEARCH PAPERS ↓

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