If anything came to surprise me about this journey, it was the sheer volume of physical pain involved. I had taken on impressive physical feats before. I had run a sub-3:30 marathon back in 2003 (my first and only attempt) after put­ting in the hundreds of training miles required. I’d done some of the most grueling weight training on offer, most of it either on the beach or at The Yard, a nearby temple of athletic performance where Maria Sharapova, Kobe Bryant and Tom Brady, among many others, have kneeled with exhaustion. But the physical toll of trying to dunk made the marathon and the semipro football and the parenting and everything else I’d ever attempted seem like mere rubber band snaps to the wrist. The lifting didn’t hurt as much as the jumping, the banging of my quadragenarian appendages into the ground, taking off and landing 50 to 200 times a day. My legs never got used to this bludgeoning, never got better at recovering from it, despite my daily foam-rollering, stretching, icing and hydrating. Even on my off days, a quick game of tag with my kids or a bike ride to the park meant daggers in my thighs and a gait like Fred Sanford’s.

Michael McKnight

I wondered: Does jumping hurt this badly when 38-year-old Vince Carter does it? Did Carter’s legs ache like this when he was 13, on the outdoor courts at Ormond Beach (Fla.) Elementary, trying and failing hundreds of times to get his first dunk?

“There aren’t many people in the world who can [dunk], that’s why it has this allure, I guess,” Carter told me last fall, during his first training camp with the Grizzlies. “As far as trying to do it, there are so many ways people can go about it. The approach you’re taking is the right approach. When I was younger, that’s how I started. Tennis ball, to the point that it became easy. Then a volleyball. Then a girls’ ball. Finally I took—it was like a dodgeball. I dunked that and said, ‘You know what, I’m gonna try it.’ Next thing you know. . . .” He shrugged and smiled, the gray whiskers on his jaw sinking into a dimple.

“How old were you?”

“It was seventh grade. No, it was sixth grade. I was, what, 12 or 13?”

Joe Fortenberry was 18 or 19 when he first dunked. “He was 6' 7" back then too,” said his son, Oliver. “He and his friends would practice on a barrel ring or a wagon-wheel ring nailed to a barn.”

“What was he like in his early ’40s?” I asked. “Was he the kind of dad, the kind of husband, who would take on something this impulsive and inconsequential and time-consuming? The kind who would make himself scarce for a few months so he could, I don’t know, restore an old car or try to hit a hole in one?”

“there’s something about dunking a basketball that lures us in,” says 1996 NBA slam dunk champion brent barry. “it stokes the imagination. it’s something you always dream of doing.”

“No, not Dad,” Oliver said in the brick tract home where he grew up. “He was an older dad, like you, and his family was the focus of his life. The only time he wasn’t home with us kids was when he went out on the road for Phillips Petroleum, buying and selling leases in western Kansas and Oklahoma. When he got back he’d say, ‘All I wanted to do was come home.’ ”

James Naismith, I learned, was a bit different. “I was only three when he passed away [in 1939],” said his grandson, James Naismith, 78, of Corpus Christi, Texas. “He was known as a tenderhearted man, but he also had”—the doctor’s namesake pauses—“the polite term is ‘firmness of mind.’ It’s kind of a family trait. He devoted his life to improving the lives of others through physical activity, through games. That took time.

“A lot of people don’t know this,” he continued, “but Granddad patrolled northern Mexico when Pancho Villa and his troops were down there. [Naismith served as an infantryman and chaplain with the Kansas National Guard.] He spent time in France during [World War I]. He had five kids at home.”

That I had abandoned my wife and children for something far less significant than world war was still bothering me. Brent Barry, who is not only a 43-year-old dad and a neighbor but also the 1996 NBA Slam Dunk champion, nodded knowingly when I brought this up over coffee last fall.

“There’s something about dunking a basketball that lures us in,” he said, reflecting on his first jam, during lunch period his sophomore year at De La Salle High in Concord, Calif., back when his driver’s license read 5' 11", 112 pounds. “It stokes the imagination. It’s something you always dream of doing. I have a friend whose father, at age 50, is trying to dunk.”