I remember the moment a few years ago while watching TV when I realized that if I were riding in the Tour de France, at age 42 I’d be the oldest person in the race. It hit me that my dream of racing in cycling’s biggest event was over…it was not going to happen.

Not that I’d been competing, let alone training seriously, on the bike for a number of years.

Or that not even in my “prime” years for competitive cycling would I have been good enough. It’s just that now I had an excuse…. I was too old, too far past my prime years.

So what happened? Is there a physiological reason people in their mid-40’s are no longer able to compete at the professional level in most sports, or is it a constellation of challenges, such as the time devoted to training, motivation, managing kids’ schedules or…