I've noticed that if I'm lifting very heavy,low reps where the bar speed is generally slow that I don't feel the benefit of the strength gains in my punching and kicking. I've actually found it's most effective staying in the 8-12 rep range. I think it's more to do with the speed the bar travels at than anything else. So I think I could lower the reps and keep increase the weight only as far as I can lift the weight easily (and quickly). I'll experiment with that at a later date. Regardless of the actual exercises (that's another issue) what do you find works best for increasing punching and kicking power?