Youth sailing.

I suspect that teenagers have a greater muscle mass or strength to overall weight ratio (or to skeleton weight) than us older folk. Back in the dark ages when I was a teenager and under 8 stone soaking wet, I played squash for a minimum of 6 hrs per week, often on my own, and hiked off what ever I was sailing all weekend. Never felt any aches or pains.

Originally posted by Chris 249 At the risk of sounding like I'm channelling Eric Twiname (which would actually be a damn good thing) I get the strong feeling that kids tend to do well partly because they play with boats. At the top end of the hottest centreboarder fleets I've sailed in, everyone still played around, whether it was in Lasers with Ben Austin (world Youth champ) when we'd do races with everyone standing on the foredeck, to windsurfers where everyone who was good would just throw the boards around for fun. I've tried to get adults to do that when coaching, but it's all but impossible. Even in windsurfers on a warm day, most adults tend to try to stay dry -  but probably not the winners. I get the feeling that at our national titles, if people are waiting for wind the people more likely to get wet are the winners, including the ex-Olympians, because they will be the ones playing around and still pushing their limits of their handling with freestyle tricks. Playing with the boat teaches your subconscious the way things like heel affect helm balance, speed and handling. Add to that the structured lessons and training kids get these days and they become depressingly good depressingly early.

Originally posted by Daniel Holman assuming you can keep the beer, kitesurfing and fanny at bay.

At the risk of sounding like I'm channelling Eric Twiname (which would actually be a damn good thing) I get the strong feeling that kids tend to do well partly because they play with boats. At the top end of the hottest centreboarder fleets I've sailed in, everyone still played around, whether it was in Lasers with Ben Austin (world Youth champ) when we'd do races with everyone standing on the foredeck, to windsurfers where everyone who was good would just throw the boards around for fun.

Yep you can apply more time, effort and parents resource in your teens all things being equal, assuming you can keep the beer, kitesurfing and fanny at bay.
Sailing is a skills and experience game, physicality is pretty secondary really but even then a few months of conditioning at any point in one's teens will make a kid far fitter than most adults will ever be.
If you participate in any racing in the popular youth classes ie oppie topper 420 laser 29er etc you will be exposed to higher quality of one design racing than most adults will ever see. This is exacerbated by the fact that excellent coaching is so freely available in the youth classes.
Plus kids are know to fear failure less ie be more progressive in their approach to performance, which underpins higher performance.
So all things being equal, if racing at all regularly in youth classes, I would say that most kids will be the best they ever will be at 17. I would say most kids in that system can cuff their dads / mums at 13.