There is nothing quite like a hit over the middle in a football game. A ballet-graceful wide receiver at full extension grabs a tightly thrown pass only to be smacked down like a rag doll by a heat-seeking safety. The play encompasses what makes football irresistible to many Americans: grace, precision, and the crushing of bone.

The National Football League has made billions from these kinds of plays, but recently took a hard hit of its own. Facing concussion-related lawsuits from more than 4,500 former players, the NFL reached a tentative $765-million settlement just days before the season's start. Most of the money will go directly to players and medical exams; a little bit, at most $10 million, will go to research.

Private research has largely led to this massive payout on the part of the NFL (still much less than could have been levied in a courtroom). Doctors like Bennett Omalu chased hunches on their own after regular working hours were over, slicing into the brains of deceased athletes to discover an unsettling reality: the hits an average football player takes add up. Over the years, as the brain is jostled by contact, it thuds into the skull, creating "tau" in the brain and initiating the disease known now as Chronic Traumatic Encephalopathy (CTE). The effects of CTE can include loss of memory, early onset of Alzheimer's Disease, unpredictable, possibly violent behavior, and sudden death from even light contact.

This is a problem that the gridiron lingo so familiar to coaches and TV commentators cannot solve. You can be heroically tough for years, but you can't, in the end, "shake off" the hits. They accumulate over months, and years, and decades, one practice and game at a ...

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