Rest Intervals for Muscle Size: Your Complete Evidence-Based Guide

Maximizing muscle growth means manipulating your training variables to create the best stimulus possible.  These variables include volume, frequency, intensity, rest intervals, and others.  Scientific research helps give us an idea of how to manipulate these variables to get the best possible results.  One common question that people have is how long they should rest between sets when their goal is muscle hypertrophy.  In this article, I will go over all of the available research to date, and provide you with recommendations based on that research.  I want to note that I will only cover studies that directly look at changes in muscle size (such as muscle cross-sectional area or thickness using ultrasound).  Studies using body composition techniques like DEXA are not sensitive enough to differences in muscle size that might occur with different rest intervals.

Key Takeaways (NEW SEPTEMBER 2019)

  • Muscle protein synthesis studies indicate little difference between 2 minute and 4 minute rest intervals when a mixture of compound and isolation movements are used. However, when rest intervals decrease down to 1 minute, protein synthesis is impaired compared to long rest intervals.
  • Most training studies that involve a mixture of compound and isolation movements show better hypertrophy with longer (2+ minute) rest intervals compared to short rest intervals.
  • Some data suggests short rests may not be detrimental to hypertrophy when small muscle group, isolation movements are used.

Practical Application (NEW SEPTEMBER 2019)

  • Most of your training should involve longer rest intervals of 2 minutes or more between sets.  This is especially true when training with moderate to heavy loads, large muscle groups, and compound movements.
  • There doesn't appear to be any advantage in to doing short rest training on legs, so you can breathe a sigh of relief that you don't need to be puking your guts out from short rest leg training.
  • Short-rest "pump" style work is best reserved for isolation movements of smaller muscle groups (such as biceps, triceps, delts, and calves).

TABLE OF CONTENTS

Rest Intervals:  The Bro Days

In the early days of bro-dom, it was believed you needed to train with short rests if you wanted to get your muscles as big as possible.  This was mainly due to the massive pump you would get from short rest training, and the belief that the pump was related to muscle growth.  This belief was further cemented when scientists such as Bill Kraemer published research showing that short 1-minute rest intervals produced greater growth hormone and testosterone responses compared to longer 3-minute rest intervals.  This idea was based on the assumption that the elevation in anabolic hormones that you get in the 15-30 minutes after a training session were related to muscle growth.  We know now, however, that post-training hormone responses are not related to muscle growth.  Thus, the idea of "train with short rest = maximal growth hormone and testosterone stimulus = maximal hypertrophy" can safely be flushed down the broilet.

Rest Intervals and Muscle Size:  Early Research

At the time that Kraemer came out with his work, there wasn't any research directly investigating the impacts of rest intervals on muscle size, so it is understandable why one might assume that short rests were best based on the hormonal responses.  In fact, it took 15 years since Kraemer's work for investigations on the impacts of rest intervals on hypertrophy to be published.  In the first study to investigate the impacts of rest intervals on size, researchers compared 2 minute rest intervals to 5 minute rest intervals on quadriceps muscle size.  While the researchers tried to equate training volume (sets * reps * load), it was 7% higher in the short rest group (the short rest group did 9 total sets per session on legs, while the long rest group did 7 total sets as they could do more weight per set).  Gains in muscle size were identical.  The problem with this study, though, is that 2 minute rests are not really that short, and certainly not comparable to the 1 minute rests that produce dramatically greater hormonal responses.  Also, training was only partly supervised.

Four years later, a study was published that compared 1 minute rests to 2.5 minute rests.  The study involved untrained subjects, and loads were chosen so that subjects only hit failure on the last set.  Statistically, there were no differences in leg size gains between the groups, but the percentage gains favored the long rest group (6.6% versus 3.1%).  Gains were also statistically greater in the arms in the long rest group compared to the short rest group (12.3% versus 5.1%, respectively).  Essentially, gains were twice as high with 2.5 minute rests versus 1 minute rest, despite greater anabolic hormone responses in the short rest group (again falsifying the "hormone hypothesis" of muscle gain).  One major limitation of this study is that subjects were not supervised during training.

In another study, researchers compared constant 2 minute rest intervals to rest intervals that were progressively decreased by 15 seconds each week from 2 minutes down to 30 seconds.  The short rest training impaired load volume, but changes in arm and leg muscle size were similar.  A follow up study by the same group showed similar results; in fact, percentage gains favored the short rest group in that study.  However, one caveat in that study is that both groups were supplemented with creatine.

Schoenfeld Saves The Day

The Hypertrophy Specialist...look at that glow...

It's hard to draw conclusions from the earlier research due to limitations in the study designs, such as lack of training supervision.  Fortunately, Dr. Brad Schoenfeld saw the limitations in previous work, and carried out a well supervised study comparing 1 and 3 minute rest intervals in well-trained subjects; I ran the statistics on this study.  Subjects did 3 whole body workouts per week, doing 3 sets of 8-12 RM of 7 different exercises (mostly compound movements) each session.  One group had 3 minute rests and the other group had 1 minute rests.  Muscle gains favored the long rest group in all outcomes, with nearly twice the gains in the long rest group in some measurements.

Brad was involved in more work on rest intervals, this time comparing 30 second to 150 second rest while using light weights (40% 1-RM) to failure.  The exercises were squat and bench press.  Muscle gains favored the long rest group for legs, but gains were similar in triceps.  One limitation of this study is that the subjects were untrained.

There's also the study comparing sets of 8 RM and 3 minute rests to sets of 20 RM and 30 second rest that I reviewed recently in the Weightology.  This study showed twice the gains in the arm muscles with the short rest/high rep training compared to the long rest/moderate rep training, which is in the opposite direction of what some of the other research has shown.  One limitation was that there was different rep ranges used for each rest interval (8 RM for the 3 minute rests and 20 RM for the 30 second rests).

Finally, there's research out there on drop sets.  Drop sets are essentially the ultimate in short rest training...they are "no-rest" sets.  I discussed a couple drop set studies in a recent research review in Weightology, and I've reviewed all of the existing drop set research in my evidence-based guide on drop sets. When training volume is high, drop sets don't provide any advantage over regular training, as long as training volume is the same (at least in the legs).  However, there is some data to suggest that drop set training might be effective for upper body isolation movements (like the triceps) when training volume is low.

Making Muscle - Effects of Rest Intervals on Muscle Protein Synthesis (UPDATED SEPTEMBER 2019)

One final piece of data that we can look at is the impact of rest intervals on muscle protein synthesis.  In the hours after a training session, muscle protein synthesis is elevated, meaning your muscles are already building new protein and going through the process of hypertrophy.  A study by Damas and colleagues compared the muscle protein synthesis response between 2 minute and 4 minute rest intervals. The subjects did 4 sets of leg press and 4 sets of leg extensions with one leg, and the same sequence with the other leg, but with the longer rest intervals. Thus, this was a within-subjects design; since each subject was compared to himself, it removes the impact of genetic variability in the training response. There was no significant difference in the muscle protein synthesis response between 2 and 4 minute rests.

Impact of 2 vs 4 min rest intervals on muscle protein synthesis from Damas et al. (2019)

One limitation here is that 2 minutes rest isn't really a short rest interval. What happens when we compare short rest intervals (like 1 minute) to longer ones? One study looked at the impacts of 1 minute versus 5 minute rests on muscle protein synthesis in the legs.  The subjects did 4 sets of leg press and 4 sets of leg extensions at 75% 1-RM to failure.  Muscle protein synthesis at 4 hours was elevated by 152% in the long rest group and 76% in the short rest group.

Muscle protein synthesis between 1 and 5 min rest intervals from McKendry et al (2016)

Intracellular anabolic signaling was also increased by 4.2 fold in the long rest group but was not elevated in the short rest group.  This study indicates that long rest training is superior for inducing muscle protein synthesis and anabolic signaling compared to short rest (1 minute) training, at least when it comes to leg training.

Taking these two protein synthesis studies together, it appears that there is little difference between rest intervals of 2 minutes or more, but when the rest intervals decrease to around 1 minute, then muscle protein synthesis (and thus hypertrophy) may be impaired when you're using a combination of compound and isolation movements to failure.

Putting It All Together (UPDATED SEPTEMBER 2019)

The following table summarizes all of the evidence I have discussed.  Grey rows represent no difference between short and long rests, orange rows represent outcomes that favor long rest, and blue rows represent outcomes that favor short rest.

Overall, most of the data favors long rest training (2+ minutes) when compared to short rest training (around 1 minute or less). There doesn't appear to be much difference between rest intervals that are 2+ minutes (e.g., 2 minutes versus 4 minutes), but you begin to see differences when rest intervals shrink to around 1 minute. The one exception where short rests may not be detrimental is when you're performing isolation movements on smaller upper body muscles (like biceps and triceps). For more info on why short rests may not be detrimental in these situations, check out this research review article.

Practical Application (UPDATED SEPTEMBER 2019)

  • Most of your training should involve longer rest intervals of 2 minutes or more between sets.  This is especially true when training with moderate to heavy loads, large muscle groups, and compound movements.
  • There doesn't appear to be any advantage in to doing short rest training on legs, so you can breathe a sigh of relief that you don't need to be puking your guts out from short rest leg training.
  • Short-rest "pump" style work is best reserved for isolation movements of smaller muscle groups (such as biceps, triceps, delts, and calves).

6 Responses to “Rest Intervals for Muscle Size: Your Complete Evidence-Based Guide

  • Travis McKinstry
    2 years ago

    Ohhhhhh the type of $hit I’d get if I referenced the conclusions this article draws… science is science!… but sometimes bro-science is more convincing for some dumb reason…

    Thanks for this!

  • erwin maasbach
    2 years ago

    I’m on a full body schedule including 8 different exercises for 3 sets. I Usually take 1 minute rest as described by one of my bros. Increasing rest from 1 to 2 minutes would mean a training time increase of 24 minutes, nearly 50%. This means my time spent in the gym would need to go up considerably. Would combining exercises in supersets help offset the amount of additional resting time, or would this negatively impact my training in another way?

    • Yes, combining exercises in supersets can help offset the additional rest time. It shouldn’t have any significant negative impact on your training, except for that some people can have trouble pushing themselves if the supersets are too close together and they are “huffing and puffing” too much and feeling too fatigued.

  • Fernando Rocha
    10 months ago

    My reading is different, we can take advantage of the growth hormone that is expressed / synthesized in greater amounts in leg exercises (or large muscle groups), and on that day do the small ones, taking advantage of the “studied” intervals: longer rest intervals in the legs and smaller intervals for small muscle groups.

    • I’m not seeing where growth hormone is shown to be elevated to any significant degree.

    • Hi, Fernando,

      The research shows that post-training growth hormone responses have no impact on muscle hypertrophy. Thus, there is no rationale to trying to design training programs to maximize the growth hormone response.

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