I like to do really fast slapping for certain songs--16th/32nd-notes and triplets (the Steve Harris influence shows through ). However, I've noticed that I seem to be working my shoulder a lot harder than my forearm when I slap, and after playing something like RHCP's "Higher Ground" or King Crimson's "Sleepless," it's very tired. Is this normal? If not, what should I do to rectify the situation? If it helps, I have my bass (Dean Edge Custom 5) strapped so that the upper horn's strap button is right over my left nipple. I am 6'2".