I'm sure this suggestion will be shrugged off like it is by most people, but you should seriously consider yoga.
One of the reasons my guitar player doesn't play live anymore is because of back problems caused by jumping around on stage with the weight of a guitar on his left shoulder for 20 years. Knowing that, I visited the chiropractor requesting some preventive information. He refused to tell me anything worthwhile, until finally he understood I didn't have insurance and couldn't regularly visit him even if I wanted.
After realizing he couldn't milk me for money, he told me yoga is the best physical activity one could do to take care of one's joints, back, circulation, and muscle. And he was right. Anytime I feel pain in my back for whatever reason, yoga will always fix it. I always notice it most when I lie in bed that night and feel how immediately comfortable I am.
And yoga certainly isn't for women only. It's not so much for building muscle, as much as it's for taking care of full body health. I know many ASU football players that take yoga and say it should be a requirement for the entire team, because it's a very different kind of difficult.
If you're interested, I can help you get a hold of the DVD I use.