Having had a dodgy back for years (I've lost track of the £1000s I've spent on osteopaths etc!?) I've have the opportunity to put my back out in many different ways.
Lamest was squatting down to pick up a coffee from the stage floor (I used to work in theatre) only for my back to go as I reached the bottom of the squat. Collapsed in agony out of sight of anyone else. Once I'd got someone's attention I ended up being stretchered out to an ambulance up a one storey high ramp (the stage was lower than the street outside). Colleagues helpfully taking the piss out of me trying to get me to laugh, which was easy as I was on nitrous oxide, without thought for the pain that the laughing was causing me. Bu**ers!
Most MTB related was bunny-hopping a big puddle. The effort caused my back to go into spasm in mid-aim. Landed in a heap. Thankfully I was out with my sister on that occasion so had someone to look after me.
There's loads more but they're the headliners. The lesson should be to look after your back! Don't just dismiss back pain as something that will go away. If back pain starts to become a regular feature of your life seek assistance. I'd recommend a combination of 30% osteopathy to 70% sports massage. Be prepared to spend whatever it takes even if it does seem ridiculously expensive. If you do not get things sorted sooner rather than later then the eventual bill and impact on your life may be much greater!
A final positive note is that exercise, especially biking, continues to be very beneficial for the health of my back. 🙂