Cleans or HI-Pulls in all forms: power, hangs, floor, etc. Rapid muscle mass gains once you get to learn proper form. A true growing exercise and very heavy weight can be used after a while. A lot of guy's fine these too much work and drop them after a few workouts, their mistake. Like the squat & DL's, you get out of it what you put into it, workout wise. Good Luck.