In reply to MikaelW:
Speaking as someone who around ten years ago went through a phase of having (literally) to crawl out of bed in the morning and pull myself upright on the nearest chair, and then struggling to get dressed as I couldn't reach my feet, I can agree with much of the advice given above. I was subsequently diagnosed with a slipped disc (L3/L4). To summarise what worked for me:
- core strength exercises, and especially Pilates
- posture (mine used to be chest forward, bum out, try standing against a wall with your heels touching. If your shoulder blades don't touch as well, your posture is wrong, rotate your hips forward)
- climbing...gentle overhangs are great, I could hang for hours just feeling that spine stretch! But yes, jumping off not a good idea
- hamstrings etc. The simple act of walking transmits shock straight into your lower back if they're tight, so get them stretched out (I can now touch the floor with my palms)
Good luck