You will do four alternating sets of four chest and back exercises in STS Mesocycle #3 Chest/Back. The exercises have been arranged in a push (chest) and pull (back) alternating order so that your working muscles will get at least 3 minutes rest between sets. With Intensities in the 80% t0 90% range it is absolutely necessary to get the proper rest between sets. In STS we have carefully measured the rest periods between sets to match the intensity level of the exercise.