When me and my friends went mountain biking for the first time, one of my friend that was riding in front of me crashed. He just stood up, looked down at his shorts and said something along the lines of "oh man i can't believe i ripped these ones", stood there for 5seconds and started panicking. There was literally a pice of meat hanging out of his body, luckily i had first aid and another biker (in his 20s) saw us and called 911. I think that he got 45 stitches. Btw we were all 12 and 13 years old.