I met my new orthopedic surgeon for the first time today (my previous doctor had retired). I got surprising news: I have sciatica from my back (Not the buttocks, like the piriformis). An MRI on my back revealed a lumbar disc herniation and spinal stenosis, right where the sciatic nerve exits from the left side. The condition is moderate, so the nerve is not compressed under normal circumstances. But anything that inflames the disc can compress the disc and cause sciatica. This explains why I first experienced sciatica symptoms about a month ago after strenuous exercise. After a few weeks it calmed down and I exploded again with more exercise. This also explains why the PT exercises I've been doing that target the piriformis and sacroiliac joints aren't as effective as they have been in the past because they don't target the lumbar spine directly. Now he's going to start me on a course of prednisone, which he thinks will help since the sciatica has calmed down a lot. As long as there are no signs of sciatica, I can do exercises, including cycling and PT exercises. I'll start increasing the intensity and decrease it as needed. I would also look into PT exercises that specifically target the lumbar area (here is a good reference). I want to strengthen the muscles in this area so it won't be so fragile in the future.