Hiya,
Have lower back problems from MTB’ing a tad bit too much. I found a remedy though I use, USE vybe or shockposts on my bike and now I’m fine. As a subnote I have three bikes all hardtails two 853’s and a titanium. The two 853’s are such so different in terms of stiffness the fisrt is a 2002 rock lobster, love it, it really absorbs bumps and trails. The other a cotic 650b super stiff to a point of ally frames…cotic is by far the fastest easiest to ride fast, but the rock lobster is still my favourite.
The titanium hmm is lovely to ride and just soaks up trails…
So in summary best to find a way of obsorbing the trails. The USE posts, OK are not current flavour of the month, but they work so well. I did try to switch back to fixed post with the cotic and my back problems returned…
Br
JeZ