appropriate period of rest time per set in exercising
When general fitness and strength is your goal then any rest period will do; just make sure that you aren’t taking too long and being an asshole by taking up equipment that other people might be trying to use.
There are more specific guidelines that you can follow, though:
When strength is your goal, you want to be able to complete quality reps at a higher intensity, this means you should taken anywhere from 2–5 minutes rest depending on the weight that you’re working with. If you’re near your 1RM weight, then the longer the rest period should be. If you’re working anywhere from 65–85% then you can probably rest 2 minutes, or even as short as 1.5 minutes.
When pursuing hypertrophy, you want to maintain metabolic stress and time under tension. With this in mind, you’re going to be using weight that is somewhere in the range of 50–75% of your 1RM, and you and definitely use somewhere from 1 -2 minutes of rest depending on the weight that you’re using. Keeping your rest periods shorter will jack up the intensity which will increase and maintain a higher level of metabolic stress.
When muscular endurance is your goal, you want to maintain a higher volume of work with a lower rest interval. With this in mind, we’re looking at rest intervals from 15 seconds to 1 minute. Again, the weight that you’re using will dictate the length of rest that you will need, as will the muscles being worked. For something like high-rep back squats, you’ll want to utilize the longer end of the range, while with something like biceps curls you can probably use 15 seconds rest intervals. The shorter rest interval can also be used for metabolic exercises like battling ropes, kettlebell swings and sprints.
Hope that helps!