The advice for people suffering simple back pain (not caused by an underlying condition) is to keep active and avoid sitting for long periods of time. It really helps if you can strengthen your core muscles to support your spine and Pilates can be a great way to learn how to engage the right muscles.
The bridge pose really works all the muscles through your lower back, bottom, and abdomen.
Here's how to do this exercise:
First, lie on the floor with knees bent, feet flat and hip-width apart.
Tighten your abdominal muscles slightly. Slowly curl your pelvic bone up and off the floor, then your bottom, creating a straight line from your knees to your shoulders. Hold for up to three seconds, then lower your bottom back to the floor and repeat up to ten times.
Maintaining good posture can also help by keeping everything in alignment. Check your normal stance by looking sideways in a mirror to make sure you’re not allowing your hips to come forward. Then tighten up your tummy muscles and try to grow as tall as you can.
via Yours UK