I have a very lightweight bass, it's not an ounce heavier than my lightweight Strat guitar. But from both of these, even from my nylon string classical, I can't play standing up for very long before my shoulder is burning with pain (where the strap rests). Now, I am a small girl and not very muscular. Is my lack of shoulder muscle the biggest reason for this pain? Will continuing to practice build up my tolerance or will it just keep hurting if I don't build more muscle? Is there some kind of padded strap which can distribute the weight better? I don't hear about a lot of people having this problem and I know I'm not the only bassist/guitarist who isn't muscular or large. Any help would be appreciated. I'm worried about what happens when I finally get in a band and can barely play through a concert without my shoulder falling off.