There's a maudlin retrospective once one receives the education to appreciate this if they in fact didn't capitalize on it when they could have. Right around puberty your heart and lungs as well as your hormone levels are over-sized, giving you athletic abilities you'll never have again without drugs. I often use random boners and zits as an adult to know I'm releasing enough testosterone to grow muscles. It's perpetual puberty.
The sad part is, most of us missed the boat on that state when we had it naturally. We sat home and worried about what our school mates thought of us. It was always the bad things we think about ourselves. Funny how that works, huh?
Dancers and gymnasts have to retire in their 20s because there's nothing for them to do for one, and their cartilage hardens, making that type of work nearly impossible. Only babies bounce. However, by our 20s and given the current influence of Healthy People 2010/2020 we have the knowledge, motivation, and time and money to workout properly if we should be so inclined. That market in this generation aforementioned created lifestyle centers placing a gym and a supermarket every 10 miles.
We have all the tools to be as fit as possible in young adulthood but the sad fact is we are trying to cook rotted meat. Many of us are far beyond help by the time we waddle our big fat asses out of our cars to walk on the treadmill.