Current resistance training guidelines recommend long rest intervals (i.e. 3 minutes) to maximize muscle strength. Alternatively, short rest intervals of around 1 minute are generally recommended for maximizing muscle growth. This is based on the premise that higher metabolic stress associated with limiting rest between sets will promote a greater muscle-building stimulus. Some have specifically pointed to acute post-exercise increases in anabolic hormones as a primary driving factor in the process.

Back in 2014, I co-authored a review paper on the topic with my colleague Menno Henselmans that was published in the journal Sports Medicine. After a thorough scrutiny of the literature, we determined that there was little basis for the claim that shorter rest intervals was beneficial to hypertrophy. As I discussed in this blog post, It would appear from current evidence that you can self-select a rest period that allows you to exert the needed effort into your next set without compromising muscular gains. That said, our recommendations were limited by a dearth of controlled studies on the topic. Moreover, no study had investigated the generally accepted guidelines of taking 3 minutes rest for strength gains and 1 minute for hypertrophy in resistance-trained individuals.

Until now…

I recently collaborated on a just-published study that investigated the effect of rest intervals on strength and hypertrophy. Here’s the scoop:

What We Did

A cohort of 21 young men were randomly assigned to either a group that performed a lifting routine with 1- or 3-minute rest intervals. All other resistance training variables were held constant. Subjects performed a typical bodybuilding-style routine that comprised 7 different exercises working the major muscle groups of both upper and lower body. Three sets of 8-12RM were performed per exercise. Training was carried out 3 days a week for 8 weeks.

We tested subjects immediately before and after the study period. Tests for muscle strength included 1RM for the bench press and back squat. Muscle-specific growth was assessed by b-mode ultrasound for the elbow flexors, triceps brachii, and quadriceps femoris.

What We Found

Maximal strength was significantly greater for both 1RM squat and bench press for the group taking longer rest. No big surprise here. Somewhat unexpectedly, however, muscle thickness tended to be greater when taking longer rest intervals as well. Although we can’t be sure of the underlying mechanisms, we speculated that results may be attributed a reduction in total volume load (i.e. reps /x/ load) over the course of the study. There is a well-established dose-response relationship between volume and hypertrophy, whereby higher volumes correlate with greater muscle growth. Thus, very short rest periods may compromise growth by reducing the amount of weight you can use on subsequent sets. This would indicate that if there are synergistic benefits to heightened metabolic stress, they are overshadowed by the associated decreased volume.

What are the Practical Implications

The obvious take-home here would seem to be that resting 1 minute between sets compromises gains in muscle size. But if 1 minute is in fact too short a rest period, how long should you then rest when maximal hypertrophy is the goal? Well, based on previous work in well-trained individuals, it would seem that 2 minutes provides sufficient recovery so as not to undermine growth.

That said, it’s important to take these results in proper context. Realize that we looked only at effects of the two respective conditions (i.e. 1- versus 3-minutes rest) on muscular adaptations. But rest interval length does not have to be a binary either-or choice. There is no reason you can’t combine different rest periods to potentially maximize hypertrophy.

A viable strategy is to take longer rest intervals on your large-muscle compound exercises such as squats, presses and rows. These movements generate very high levels of metabolic disturbance, particularly when performed with moderate rep ranges (i.e. 8-15 reps). Thus, longer recovery periods are needed to fully regenerate energy levels for your next set so that volume load is maintained across sessions.

On the other hand, single joint movements are not as metabolically taxing and thus you’re able to recover more quickly from set to set. Exercises like biceps curls, triceps pressdowns, and leg extensions therefore could conceivably benefit from shorter rest periods. In this way, you can heighten metabolic stress and its potential hypertrophic benefits without negatively impacting volume load. In this scenario, it’s best to keep the short-rest sets at the end of your workout to ensure they don’t interfere with recovery of compound exercise performance.

A final word: Research is still emerging on this topic. Each study is simply a piece in a puzzle. As more studies are carried out we’ll hopefully develop a better understanding of how programming can be tweaked to maximize the growth-related response. Stay tuned.