The best between-set rest interval to promote maximal muscle growth has long been debated. Some argue for short rest intervals to promote greater metabolic stress. Others contend longer rest intervals are better to achieve more force production and tension in subsequent sets. This new study from Singer and colleagues systematically reviewed the existing scientific literature and the researchers performed a meta-analysis to better understand the magnitude of effects between-set rest intervals exert on measures of muscle hypertrophy.
Overview
- What did they test? The researchers systematically reviewed the scientific literature to identify studies that compared the effects of different rest intervals between sets of resistance training on measures of muscle hypertrophy. After identification of studies, the researchers performed a meta-analysis to determine the magnitude of effect between different rest interval conditions on measures of muscle hypertrophy.
- What did they find? After identifying only nine studies meeting inclusion criteria—mostly in untrained young men—greater hypertrophy appeared to occur when rest intervals were at least 60 seconds between sets. The magnitude of hypertrophy varied considerably in studies involving more than 60 seconds of rest between sets. While the results tended to favor rest intervals ≥60 seconds for both the arms and legs, the differences in measures of muscle hypertrophy compared to rest intervals <60 seconds were relatively small.
- What does it mean for you? If your goal is to maximize muscle growth, resting at least 60 seconds between sets appears to result in slightly more muscle growth than shorter rest intervals. Since most participants included in the meta-analysis were untrained, caution with interpretation is warranted in applying these findings for highly-trained individuals. Based on the findings of this meta-analysis and a small number of others on auto-regulated or "self-selected" rest intervals, letting yourself decide how long to rest between sets might be just as effective, or even superior, for muscle growth instead of using a fixed rest time.
What’s the problem?
A limited number of prior studies suggests inter-set rest intervals can influence muscle growth in response to resistance training 1 2. The National Strength and Conditioning Association has recommended rest intervals of 30-90 seconds between sets to optimize hypertrophy 3. This has been argued to promote elevations in hormones important for increasing anabolic signaling. However, the transient elevations in hormone levels in response to resistance training have been reported to have little effect on muscle hypertrophy 4. Additionally, shorter rest intervals can reduce the number of repetitions performed in subsequent sets which could reduce the volume of training performed across time 5. To this point, Mckendry and colleagues reported blunted muscle protein synthesis responses to training when rest intervals were limited to one minute as compared to five minutes 1. Therefore, the authors of this new systematic review and meta-analysis aimed to clarify the effects of different inter-set (between-set) rest intervals on measures of muscle hypertrophy.
Purpose
The purpose of this study was to systematically review the scientific literature and perform a meta-analysis on the effects of rest interval duration during resistance training on measures of muscle hypertrophy.
Hypothesis
This was a meta-analysis to determine the magnitude of effect between different rest interval conditions on measures of muscle hypertrophy from the available scientific literature that met the researchers inclusion criteria. So, no hypothesis was provided.
