After decades of martial arts, weights, extreme sports and doing every stupid thing that I could find... I actually fucked my back stretching LOL.
I have always stretched and am quite flexible, standing I can put my hands flat on the ground, do the splits etc. One morning I was stretching down and couldn't quite stretch as far as usual so I pushed it and then suddenly felt something bad in my back... turns out pushing that stretch, I caused the L4-L5 and L5-S1 bulges.
It turns out that most of my muscles were nice and loose except one which is an absolute bastard to target, the psoas muscle. Long story short, felt like I was being stabbed in the right asscheek, every time I stood up and my right leg even went numb... kinda shit :-(