1. You don't have to take a fistful of vitamins... A shortage of Magnesium is what causes most muscle cramping. Take a magnesium cap and as was already mentioned, drink lots of water. Before a gig, I always take a B-12 (endurance, stamina,) and I always have a jug of water or 'sport drink' right behind my throne. Between numbers, I'll sip on it. Gets me through 3/4 hour long gigs.
2. If you're suffering from any impact related injuries or problems... fix your technique and you'll fix the problem. Impact problems arise from holding the sticks too tight. The impact from the blow travels up the stick and into your hand. Lighter grip is the answer. Good way to check yourself to see if you're holding onto the stick too tightly is; as you play, see how much movement is happening at the back, butt-end of the stick. If the butt-end of the stick is moving up and down freely in your hands, then your grip is on the money. No movement, or little movement of the back end of the stick and you're holding on too tight and causing the force of each blow to reverberate through the muscle and bone of your hands.
Simple ergonomics. Remember magnesium to prevent muscle cramping.
John