I went for a long warmup to a race several years ago. I waved to friendly people while still running on a sidewalk that had a flagstone uprooted by a tree. I tripped on this and fell. I went to a specialist about it, and he told me to stop running for a while. I ran anyway with a black sling. This was silly in retrospect. I eventually healed. By the way, I did run that race, and I did quite well. I believe that it was the adrenaline caused by the fall. Thanks for reading.