I do alot of mountain biking, so I'm used to scrapes, bruises, and falls. but most of these result from low speed. crashes. The worst crash I've ever had was on the MUP while crusin' at 15mph. Ran over a stick the size of a hotdog. Next thing I know I'm over the bars with two cracked ribs and a badly bruised shoulder.
When I got up and checked to see what happened, I saw that the stick had jumped up and lodged itself perfectly between the brake pad and the front rim (only one end of the stick was sharp enough and shaped just right to fit).
Beware of the small sticks.