Eliminating, reducing or modifying the interval regime is in order for sure. I’ve worked closely with my PT in the past with great results, but this back issue has flipped the script. A stretching and strengthening regime that accompanied the cycling/spinning 3 yo, now has components that piss off the back, so all of that has to be questioned. Hard intervals and some core exercises piss off the back. I still do 100-150 miles back to back even with compromised fitness, but I need to get that fitness back. I will for sure meet with my a PT and craft a plan, but wanted to see what worked/didn’t work for others.