I often get asked how much time you should spend resting in between sets, and while what works for different individuals will vary, I’ll briefly talk about the science behind it to help guide you towards a rest period that works best for you and your goals.
I thought about writing this article a couple of weeks ago when Costin, an old gym buddy of mine came up to work out with me and my regular gym buddy, Eric. Costin and I and another friend used to work out together religiously. We spent a lot of time in between sets because there were three of us and to top it off, we’d do a lot of chatting and arguing. We’d probably spend about 3-5 minutes in between any given set. So when Costin was recently talking about 75 second rest periods, it sounded way too short to me, although later when i reflected on it, I realized that when Eric and I work out (while we still do a lot of chatting) we probably rest only about two minutes or less — and with Eric over the last six months, I’ve been making some really big gains in strength. This might just be circumstantial, but it’s definitely food for thought.
When you rest less than two minutes between sets, you are using something called the “lactic acid energy system”. This is a medium duration energy source and is the primary energy source used in most body building workouts. If you rest longer than three minutes between sets, you are using more of the “ATP-PC energy system”. This is the most powerful energy system for short bursts of exercise. There isn’t a switch that turns off one of these systems and starts the next at the two or three minute mark. These systems overlap and work together to handle the workload.
Taking rests that last longer than two or three minutes will use more of the ATP-PC energy system, and allow your muscles to be almost completely replenished to lift another heavy set and max out the muscle. While this rest time will keep you moving big weight, there are other things to consider. By keeping rest periods under two minutes, the lactic acid energy system is not able to replenish the muscles as quickly, but by training with these shorter rest periods during the workout, there will be increased levels of growth hormone in the blood after the workout to promote muscle growth.
So your rest period depends on a few different things, most importantly what feels right to you and what you see the best results with. I think a two minute rest cycle is a good place to start and you can make adjustments either up or down from there. Other things to keep in mind are that smaller muscle groups take less time to recover than larger ones, and testosterone production drops off sharply after 45 minutes, so you want to keep you entire workout within that time frame.