I can tell you that when I'm exiting a flare and bleeding stops, if I exercise too vigorously, or if I do too much abdominal exercise, I'll start bleeding again. If you think about it, inflammation makes the tissues more swollen, more loose, more watery. The blood vessels get more delicate. Then you go running which adds agitation. It's like tossing around a water balloon, it eventually breaks.
I feel like the bowel blood vessels in people with active IBD are really delicate and can be broken easily.
The first time I became aware of this was after my first flare. I started taking yoga classes and after the first class I started relapsing. Had to re-start prednisone and everything.
Yes, that makes sense. I don't want to stop running though. I will try to keep it at an easy pace until things calm down.