[L]ate last month the University of Michigan’s Institute for Social Research released the findings of an N.F.L.-funded phone survey of just over a thousand randomly selected retired N.F.L. players—all of whom had played in the league for at least three seasons. Self-reported studies are notoriously unreliable instruments, but, even so, the results were alarming. Of those players who were older than fifty, 6.1 per cent reported that they had received a diagnosis of “dementia, Alzheimer’s disease, or other memory-related disease.” That’s five times higher than the national average for that age group. For players between the ages of thirty and forty-nine, the reported rate was nineteen times the national average. (The N.F.L. has distributed five million dollars to former players with dementia.)

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In 1905, President Theodore Roosevelt called an emergency summit at the White House, alarmed, as the historian John Sayle Watterson writes, “that the brutality of the prize ring had invaded college football and might end up destroying it.” Columbia University dropped the sport entirely. A professor at the University of Chicago called it a “boy-killing, man-mutilating, money-making, education-prostituting, gladiatorial sport.” In December of 1905, the presidents of twelve prominent colleges met in New York and came within one vote of abolishing the game. But the main objection at the time was to a style of play—densely and dangerously packed offensive strategies—that, it turns out, could be largely corrected with rule changes, like the legalization of the forward pass and the doubling of the first-down distance from five yards to ten. Today, when we consider subtler and more insidious forms of injury, it’s far from clear whether the problem is the style of play or the play itself.

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In one way or another, plenty of organizations select for gameness. The Marine Corps does so, and so does medicine, when it puts young doctors through the exhausting rigors of residency. But those who select for gameness have a responsibility not to abuse that trust: if you have men in your charge who would jump off a cliff for you, you cannot march them to the edge of the cliff—and dogfighting fails this test. Gameness, Carl Semencic argues, in “The World of Fighting Dogs” (1984), is no more than a dog’s “desire to please an owner at any expense to itself.”

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Professional football players, too, are selected for gameness. When Kyle Turley was knocked unconscious, in that game against the Packers, he returned to practice four days later because, he said, “I didn’t want to miss a game.” Once, in the years when he was still playing, he woke up and fell into a wall as he got out of bed. “I start puking all over,” he recalled. “So I said to my wife, ‘Take me to practice.’ I didn’t want to miss practice.” The same season that he was knocked unconscious, he began to have pain in his hips. He received three cortisone shots, and kept playing. At the end of the season, he discovered that he had a herniated disk. He underwent surgery, and four months later was back at training camp. “They put me in full-contact practice from day one,” he said. “After the first day, I knew I wasn’t right. They told me, ‘You’ve had the surgery. You’re fine. You should just fight through it.’ It’s like you’re programmed. You’ve got to go without question—I’m a warrior. I can block that out of my mind. I go out, two days later. Full contact. Two-a-days. My back locks up again. I had re-herniated the same disk that got operated on four months ago, and bulged the disk above it.” As one of Turley’s old coaches once said, “He plays the game as it should be played, all out,” which is to say that he put the game above his own well-being.