Simple fact in building muscle. Activate deep muscle fiber, pump blood into muscle, and stretch. Example: incline press, 10 rep max, 30 second rest, 8 reps, 30 second rest, 6 reps, 30 second rest, 4 reps, 30 second rest, 2 reps, (deep muscle is activated). Drop weight and rep out, (blood pumped into muscle). Incline DB fly's two sets 20 reps, (muscle stretched). I have used this principle with the greatest success. HST sounds good for a neophyte. However any hardcore bodybuilder could do that HST routine in about 15-20 minutes. When you are only doing 8 to 12 exercises, if each exercise took one minute, still you would have another twelve minutes of rest. HST just doesn't make sense to me.