Took a tumble six weeks ago and have been dealing with the fallout on and off since then. The latest flare up was last Tuesday when I tried some faster intervals and my ribs felt really sore afterwards. Wasn't sure If it was anything serious or not so checked it out with my GP but the conclusion was that it's muscular -skeleto.
It eventually dawned on me that getting it checked out by a physio would be a good idea. They have a great way of figuring out where to prod to cause the most pain!
Anyhow, seems I've damaged my lumbar joints. The good news is that, given one to two weeks rest, it should settle down. It's just a shame that I didn't visit the physio much earlier (I didn't because I thought it was minor bruising, then organ damage then it seemed to clear up).
So, I now need to do some exercising that doesn't twist my spine. Might try some swimming (although I haven't done that for years).