Well written and researched look at the physical decline of athletes, baseball players in particular, Jeter specifically.

I don't think the paywall will be an issue.

Snip:
At 90 miles per hour, average major-league speed, a baseball leaves the pitcher’s hand and travels about 56 feet to home plate in 0.4 seconds, or 400 milliseconds. The batter’s eyes must first find the ball, Adair writes, then sensory cells in the retina encode information on its speed and trajectory and send it to the brain. This all takes about 75 milliseconds, during which the pitched ball has traveled nine feet.

The brain then sends messages through the spinal cord that tell muscles to initiate the swing. Adair writes that the first such messages go to the batter’s legs to prompt him to step into the ball. (Jeter, at the beginning of this season, tried to hit without a stride. Instead of making his own actions quicker, he basically tried to buy himself some milliseconds by retraining his brain to skip the first part of the swing process. He wasn’t comfortable with it and is taking a stride again, though it’s a short one.)

The batter continues to track the ball as muscles in his arms and upper body begin to bring the bat around, but once the pitch is halfway to the plate, it is too late for him to change the swing plane. He must instantaneously form a mental picture of the ball’s course, then direct his swing to where he believes it will be. This is why batters are fooled by sliders and other pitches with so-called late break. If it weren’t "psychologically upsetting," Adair writes, a hitter could just as well close his eyes once the ball is halfway to the plate and get the same result.