But there are also athletes like Brady: If he avoids a major injury, I would not be surprised to see him playing in his late 40s. With modern rule changes that are friendly to the passing game and unfriendly to beating up on quarterbacks, there’s no reason he shouldn’t be able to maintain or even improve his perceptual skills. Each play is a flashcard that teaches a QB to read the field intuitively like a chessboard. As Brady put it after the Super Bowl, his job is “not as hard as it used to be.”

Clearly, though, I was not going to pick up quarterbacking as my new skill for the year. Joyner sent me a paper about a Danish rower who won a medal in five straight Olympics between ages 19 and 40, and for a moment I thought about trying rowing. But beginning as a rower in Brooklyn felt tortuous. I wanted to start with something simple that I could do anywhere.

I stumbled upon a YouTube video on the “planche,” a gymnastic move. You put your palms on the ground and suspend your body parallel to the floor. It seemed challenging and fun — I was sold.

I was a runner in college, and have continued that exercise, but I would need to regain some upper-body strength to manage a planche. I started with a strength routine I used to do with a college teammate after runs: a push-up pyramid. One person does a push-up, and a partner follows suit, and then the first person does two, and so on up to some number and back down to one. It involves 100 push-ups at minimum, and you have to wait in the up position while your partner takes his turn. If he gets tired, you spend a long time in the up position waiting to go. I was going to make it a little easier in my old, post-Phelpsian mid-30s, by just counting out the push-ups my partner would have done, without accounting for him getting tired.

I turned on some motivational music — the “Serena Williams’s Spontaneous Speed” album, of course — and got to work. I was about halfway through my first pyramid (going up to 10 and back down) when I realized I was feeling something more than simple fatigue. I kept going, and pretty soon realized something in my shoulder was definitely not right, so called it a (very unsatisfying) day.

The next morning, I needed help slipping into a shirt, and couldn’t rotate my shoulder back far enough to put a jacket on. (Thankfully, it was summer.) I had strained my right rotator cuff, and would be getting dressed with only my left hand for the next month. It’s an injury more often suffered by elderly people who use their arms to get out of a chair.