When I began this form of interval training, if I was doing 3 sets of 15 repetitions of a bench press, I would leave exactly 45 seconds between sets. If I was doing 3 sets of 12 repetitions with heavier weights, I would need 50 seconds between sets, if my sets were 10 reps I would take 55 seconds, and if I was lifting heavy weights, at 3 sets of 8 reps, I would take one minute between reps. This is a good baseline for an average athlete to work with.
