Does rest time vary depending on the exercise or muscle group? For example, do compound exercises require greater rest time than isolation exercises?

Question

I'm curious if rest time varies depending on the exercise.

I certainly feel more tired after doing a compound exercise like squats compared to an isolation exercise like a leg press, both of which have a similar purpose.

I would assume that each individual muscle needs a rest time minimum depending on your goals of strength training or hypertrophy training, as it needs to time to resynthesize glycogen and ATP. So for strength training, that is 3-5 minutes, and hypertrophy training, that is 30-60 seconds.

However, most sources don't go over the differences between exercises. I notice that I can perform isolation exercises with the same number of reps on isolation exercises like a bicep curl after just 2 minutes (I'm strength-training) and lift the same weight, but I cannot do so for for compound exercises like a squat, which I prefer 4 minutes.

The bicep curl mainly uses the bicep, a smaller muscle. Squats on the other hand active multiple leg muscles like the quadriceps, hamstrings, calves, among others, all of which are large muscles, at least compared to the bicep. I wonder if rest time is affected by the total muscle mass of the muscles involved/the exercise, like the body takes longer the more muscle mass involved, or each muscle is independently recovered.

If each muscle independently recovers, that would mean you could probably do squats and then go straight into bicep curls with no rest, where your leg muscles are possibly "resting" while you do bicep curls. This isn't something I have tried before.

Answer 1

You halfway answered your own question: isolation exercises use single muscles and thus your body only needs to replenish the glycogen and ATP for one muscle. For compound exercises it are multiple, so indeed it might take a bit longer. Also there is a load on the central nervous system which requires some recovery.

I tried to find some relevant resources on it, but sadly most research only seems to focus on the big picture. And I can't find any proper correlation on the time to recovery vs the amount of muscles used.

tl,dr is: More muscles require more resources for recovery.

From personal experience for compound exercises I like to take 3-4 minutes (depending on how I feel) and for isolation exercises I like to take 1-2 minutes. So the same as you actually. I've been training for more than 15 years and except the last few years dealing with some injuries this has always worked very well for me!

Answer 2

Your Assumption is pretty much spot on, rest times should be longer on compound movements. this is not only because compounds involve multiple muscles that need to recover, but for that reason they are usually also more taxing on the cardiovascular system, so it takes your heartrate longer to return to baseline. as for your final paragraph, this is definitely something you could to to be more efficient with your time at the gym, the performance on your secondary exercise should not drop drastically provided you are using an isolation exercise that works a different muscle than the first exercise, however this is not something i have ever implemented in my training so i can't really speak from experience here.