the chest, triceps, shoulders are the primary muscles, if you will. however, more of your power comes from your hips, so your abs and obliques do a lot of the work too. so do your legs. and, if your technique is proper (or even if it isnt) your back is involved, and of course your biceps. so to review: chest, shoulders, triceps, abs/core, back, biceps, legs. a whole-body weight training regiment will help with those punches, but make sure youre practicing punching too.