Another simple question with a complex answer. Here, we chat with Form Nutrition about some of the studies that investigate this and come up with some useful guidelines…
We’re lucky in that recently a team including Brad Schoenfeld carried out a systematic review on this very question. For those that don’t know, a systematic review looks at all the studies on a particular question that meet some criteria. In this case they looked at all published studies longer than 4 weeks that measured muscle mass and compared rest intervals less than 60 seconds to rest intervals greater than 60 seconds where subjects were healthy and injury free. From an initial cohort of over 1000 studies the criteria narrowed it down to just 6.
So what did they find? At a very high level it looks like longer rest periods, i.e. more than 60 seconds, seem to favour hypertrophy (muscle growth) when compared to rest periods shorter than 60 seconds. Why? Simple really; more rest enables a higher total volume.
Digging deeper, results are more nuanced when you look at trained and untrained people. Trained people (those with a decent amount of strength training under their belts) are almost certain to benefit from longer rest periods. Untrained people, i.e. newbies, seem to make good progress regardless of rest period. Perhaps not surprising when you consider the concept of ‘newbie gains’.
The final piece of the puzzle to understand is intensity. Working to failure (the concept of repeating an exercise to the point where you reach your limit and have to stop), the research favours longer rest periods simply so you can recover and lift heavy again next set, keeping total volume high. The corollary being if you’re not working to maximum intensity or failure, shorter rest periods are sufficient.
So how to implement in your training?
- if you’re relatively new, don’t worry too much, rest as you need, lift and gain experience.
- if you’re well trained, lift to failure and use longer rest periods, 2-3 minutes.
A final note on structuring workouts, the researchers suggest:
“The best approach to a hypertrophy based resistance training session may be to focus on training volume by performing complex, multi-joint exercises and incorporating longer inter-set rest intervals in the first part of the training session, and then shift the focus to inducing a greater metabolic stress by performing isolation exercises and incorporating shorter inter-set rest intervals towards the end of the training session.”
Happy resting (and lifting)!
Grgic, Jozo & Lazinica, Bruno & Mikulic, Pavle & Krieger, James & Schoenfeld, Brad. (2017). The effects of short versus long inter-set rest intervals in resistance training on measures of muscle hypertrophy: A systematic review. European Journal of Sport Science.