...I used to run a 4.8 forty-yard dash
...I used to have 6% body-fat while weighing 235 lbs.
...I used to be a top prospect in American Football
But now, 23 year laters, I couldn't even do a single push-up at the moment-- yeah, yeah, that's more because my left upper arm is broken from snowboarding than and real physical decrepitude, but still...
The point is, ladies and gents: enjoy your youth. Speaking as one of the senior Escapist community members, I can tell you from experience: physical effort gets more difficult as you age, and it doesn't matter what kind of athlete you are.
Parkour, snow-sports, track & field... our bodies move in a different direction as we get older. It's a genetic imperetive.
So enjoy your youth-- in fact, fucking exult in it... because it won't be there forever.