Dads don't bounce

Josh has a skateboard. So do I. The trouble is, he's 9, I'm 40. Add to this the fact that I didn't skateboard much beyond my mid-teens, and was pretty rubbish at it even then, and you can see where this is going! Obviously then, I am the ideal person to coach Josh in the rather mundane skill of going down a curb. Mundane that is if you're one of those people who can do gravity defying leaps on a board, and clever things with rails. Me? I don't remember getting to the 'going down a curb' stage at my teen peak! So I crash out big time. But get up and back on the board obviously: got to keep up appearances. The blood (and pain) emanating from my left thigh soon becomes unavoidable though, as does the increasingly immobile nature of my left elbow (ex-physio wife is 'pretty sure it's not broken', which is reassuring!). So my question is, any other parents (needn't just be blokes, though I have a feeling...) out there who've done similarly disastrous things that, with hindsight, they should've known better about doing?