Hypertrophy, Strength Training
February 5, 2016
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.
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In the starting strength program, trainees are advised to rest much longer between heavy work sets. 8 to 10 minutes is not considered unreasonable for 5×5 squats. This makes for very long workouts, but many claim it is critical to the effectiveness of the program. Have there been any studies to look at these very long rest intervals.
Comment by Craig — February 5, 2016 @ 2:27 pm
No research I’m aware of has investigating rest periods of that length.
Comment by Brad — February 5, 2016 @ 7:01 pm
Ah, but what if you have a fixed time period for working out? Wouldn’t a shorter rest interval allow one to do more sets or even exercises, thereby increasing total volume?
Comment by Coolyyo — February 6, 2016 @ 11:25 am
Awesome study Brad. I love how you sum it up: “very short rest periods may compromise growth by reducing the amount of weight you can use on subsequent sets.”
Comment by Etienne Juneau, PhD — February 6, 2016 @ 1:32 pm
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Cheers Etienne!
Comment by Brad — February 7, 2016 @ 7:22 am
Coolyyo:
Yep, that’s true. There could potentially be a tradeoff in recovery from the higher training density, but this really hasn’t been studied. Certainly an option.
Comment by Brad — February 7, 2016 @ 7:24 am
Great study Brad. Maybe in a subsequent sets the % of decrease ( e.g. fatigue index) measured by number of repetitions drop compared to different rest interval would be good indicator of muscle strength/hipertrophy adaptation? My point is that the drop of your repetitions number will inform you to stop the training if muscle strength is your primary outcome or to lengthen your rest interval? You could do a new test for optimal rest interval for strength and hypertrophy if we know how many sets or repetitions we can do with some fixed load??
Comment by Amit — February 7, 2016 @ 8:47 am
So to speculate if the higher the exercise’s muscle fiber recruitment, the longer the rest interval needed. Would a subjects metabolic recovery capacity be the limiting factor in determining the rest interval needed to maximize hypertrophy? So could a well trained subject could get the same hypertrophic stimulus from less recovery time than an untrained subject? Because of a better metabolic efficiency from longer training experience.
Comment by Danny — February 7, 2016 @ 10:15 am
Danny:
Yep, that is a working hypothesis. Note however that the subjects in our study were resistance-trained men. Now perhaps if they were acclimated to performing sets with short rest the adaptations over time associated with buffering capacity might allow for greater preservation of volume load. If so (and there is some evidence to that effect), then it could provide a basis for using shorter rest.
Comment by Brad — February 8, 2016 @ 7:42 am
I think you summed it up well suggesting a mix. Go heavy at the beginning. Take the rest you need. Then finish with lighter weight isolation exercises and less weight.
Comment by Jason — February 8, 2016 @ 2:51 pm
Hi Brad, great summary of the study and very interesting results. I was wondering what kind of rest intervals the subjects were accustomed to prior to the study. Could some of the effect observed be due to the shift in routine?
Comment by Tom — February 10, 2016 @ 11:43 am
Tom:
I did ask subjects before the beginning of the study about the specifics of their routines. Many claimed to take short rest (60 secs or so) but when these subjects actually were timed for their rest periods it was apparent that wasn’t the case.
Comment by Brad — February 14, 2016 @ 8:05 am
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If total volume is potentially the main differentiator between the two results, I’d be curious to see what would happen if that were maintained between both groups. So one group does 3 x 10, with three minutes rest between sets. The second group does sets of 10, 8, 6, 3, 2, 1 (for example), with one minute of rest between sets, and using the same weight for each set. In this case, the second group completes the same volume in slightly shorter time – six minutes total rest for group one vs five minutes for group two.
Comment by Drew — March 3, 2016 @ 2:52 am
Drew:
Sure, there are many different ways to look at the study and that certainly would be an interesting follow-up. The fact that the shorter rest condition is much more time efficient has important implications depending on what your goals/needs are.
Comment by Brad — March 3, 2016 @ 9:20 am
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I have ALWAYS used 3-5 minutes between sets because if i took any less, then reps would fall sharply on my next sets. Good to know about this study.
Brad, will ever make a study about 1 set training? Obviously, multiple sets is superior, but I hear that 1 set can give pretty good results too. Thanks to you and the pre/post lifting stats that you post, I have an idea of what to expect with 3 set training, but I don’t know what to expect with 1 set training. Any ideas? Thanks.
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