I found success doing calisthenics. it teaches proper form and injuries are far less common than weight lifting, which seemed risky doing when I had back trouble. I've been able to build up my glutes and back muscles (and the entire posterior chain) in a slow steady progression. strengthside on youtube was my start. they have some great videos on the subject. from there I joined a calisthenics/bodyweight program and also just hit the local playground and hop on the monkey bars or whatever.