I'm in my 30s, but get most of my exercise from cycling, which doesn't exercise the back much. My back pain problems have been increasing over recent years, but I've had good success in the last few months with 15-20 minutes a night of yoga. I'm doing regular plank, bridge, locust, and downward dog poses for back strength, and cat/cow, sphinx, and forward fold poses for back stretches. I like a lot of the leg and hip stretches, too.