none, i've been lucky. i've got a snowboarder friend who decided to try a rodeo one day off of a jump we built, he made it around, the board slipped out from under him, and he was KOd. funny thing was we were laughing at him instead of helping him (we didn't think he was actually hurt even tho we saw him hit) and he doesn't remember a thing. another one of my friends went off the jump but we threw a snowball at him from the side, and it hit him in the head so it knocked him off balance and he rolled for a while and got a concussion. same guy had a massive yardsale, everything came off, skis, poles, helmet, gloves lol, and he got a concussion from that 2. so none for me, and a whole bunch for my friends.