Designing effective workouts is very complicated, and the scientific knowledge in this area is constantly increasing and evolving. Selecting the right exercises and choosing the most appropriate poundages to lift is obviously important. But another critical element that you may not think is very important is the amount of rest period between sets. Altering the time of rest between sets has dramatic effects on the use and replenishment of energy systems, particularly the anaerobic energy systems. Most important here is the
is depleted by a set of resistance exercise and this is associated with fatigue. After a set phosphocreatine replenishes, but it takes 2-3 minutes for near full recovery. If rest periods are too short, phosphocreatine is not fully restored and you will likely not be able to perform as well. Just how much does rest period affect the workout. In a recent study subjects performed four sets of bench press and squat exercise using 1, 2, and 5 min rest periods. They were asked to perform as many repetitions as possible on each set. The 5 min rest period condition resulted in the highest volume completed followed by the 2 and then the 1 min rest period trial. subjects completed 9 more reps over the four sets with 5 min rest compared to 1 min rest periods. This increase in training volume with longer rest periods has the potential to translate into greater adaptations to training.
Willardson JM, Burkett LN. A comparison of 3 different rest intervals on the exercise volume completed during a workout. J Strength Cond Res. 2005 Feb;19(1):23-6.