If I need lots of water, I wear the Camelbak, but if I only need 20 oz, I'll wear my water belt (water bottle on belt thingy). The Camelbak has never bothered me, no motion on my back, but the sloshing sound drives my DH crazy when he runs with me. It doesn't bother me. Sometimes on the trail I run around here I wear my bottle belt, but stash an extra one, and loop back to get it when I run out of the one I'm carrying.