In a new study out of the University of Birmingham, researchers unveiled something surprising: Conventional short rest intervals can impair the processes that control muscle growth, while extended rest intervals between sets of weight lifting can supercharge them.
In the study, published in Experimental Physiology, 16 men completed resistance exercises with either one minute or five minutes of rest between sets. Researchers collected muscle biopsies 0, 4, 24, and 28 hours post-exercise, which they analyzed to determine levels of "myofibrillar protein synthesis" (MPS) and "intercellular signaling"—both of which have a profound effect on muscle growth since you need your muscle protein synthesis to outweigh muscle protein breakdown, and your body to effectively signal slow- and fast-twitch muscles when you work out.
The men who took longer rest periods experienced a 152% increase in MPS in the early part of recovery compared to the men who took short rest intervals who only saw a 76% increase. That's a two-fold difference.
"With short rests of one minute, though the hormonal response is superior, the actual muscle response is blunted," lead study author Leigh Breen explained in a press release. "If you're looking for maximised muscle growth with your training programme, a slightly longer interval between sets may provide a better chance of having the muscle response you're looking for."
If you're just starting out with a weight-training programs, take sufficient rest of at least 2-3 minutes between sets.
"For experienced lifters, it's possible that they may not experience the same blunted muscle building response to short rest intervals, particularly if they have trained this way for a prolonged period and adapted to this unique metabolic stress," Breen adds. "Nonetheless, similar recommendations of 2-3 minutes between sets should help to ensure maximal muscle growth in well trained individuals."
If you feel like you're hitting a muscle-building plateau, gradually decrease your rest periods, the researchers recommend.
Up next on the docket: The research team will launch a followup investigation to see the effects of longer rest over a number of months, as well as how lifters can maximize their training outcomes by manipulating rest.