Rest-pause is an old-school bodybuilding technique of performing a set to failure, resting a few seconds, then squeezing out more reps. The idea is simply to get a little more work in even after the muscles have been exhausted.
Like most bodybuilding strategies, there isn’t a lot of hard science to support it, but last October the Journal of Sports Medicine and Physical Fitness did. Seventy-nine subjects with training experience were divided into three groups. One took sets to self-determined failure, others were goaded to work till they couldn’t do another rep, and the third used a rest-pause (five to 20 seconds). The ones who stopped their sets when they wanted had insignificant results. The rest-pause group saw good gains in body composition, but those who only went to failure (where they couldn’t do more) had the best gains.
The take-home? Rest-pause has value, but the bigger lesson is that pushing yourself and taking the muscles to failure is necessary to change your body, at least when you’re beyond the beginner stage.