I start to run in 1973 on a track above the basketball court at the McBurney YMCA in New York City. Twenty laps to a mile. T-shirt, cutoff jeans, denim sneakers with orange laces — flat and heavy, like low-cut basketball shoes.

The Y sells a lap counter, a metal gizmo that fits into my palm: one click for each time around. Using it means I no longer have to count the laps, and my mind can wander while my legs do the work. I can be both of my body and apart from it, present and far away.

Before I stepped onto this track, I thought of myself as unathletic. Hadn’t ever played sports. There were no teams for girls in my big suburban high school, only gym class, with its daunting pommel horses I could not mount and ropes I was afraid to climb. Never the absolute last to be chosen but one of the stragglers, a restless, fumble-fingered klutz in an ugly blue gym suit.