It was a question about soccer that got Philip Bayly interested in brain injuries.Bayly, a mechanical engineer at Washington University in St. Louis, was approached by several doctors who wanted advice about some young soccer players they were treating.
"They said, 'Well, we've got some kids who have concussions and they want to know if they can go back to play. And we don't know what's happening to their head when they're heading a soccer ball,' " Bayly recalls.
Does a header have a big effect or a small one? The doctors thought Bayly might have the answer.
"I said, 'That's really interesting. I play soccer and my kids play soccer, and I don't know what's happening when you head a soccer ball either,' " Bayly told them. "But I know how we can find out."
So in the early 2000s, Bayly brought soccer players into his lab to figure out precisely how much acceleration their heads experienced when they headed balls hurled at them by a machine.
The answer was 15 to 20 times the force of gravity, a relatively minor impact.
"Jump up and down you're feeling maybe 4 or 5 G's when you hit the ground," Bayly says. "When you play football, you have a hard collision with someone else, it's maybe 50 to 100 G's."
But Bayly realized these numbers didn't mean much unless he knew how much of this force was reaching a person's brain. So he spent the next decade trying to figure that out.
It's an effort that has involved jiggling and jarring a lot of living human brains.
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