The potential for repeated brain injuries was perhaps best exemplified by the Parkinson's symptoms suffered very publicly by the boxer Muhammad Ali. But, within the academic world, a growing body of literature has indicated that repeated concussions may carry significant risks, both for young athletes and seasoned professionals. (Although not every study has shown a significant effect on all aspects of cognitive function.)

Of course, professional sports are big business, which raises some difficult questions. Do leagues that make many of their players very wealthy owe them anything beyond that? Are fans and businesses that expect hard-hitting action complicit in the long-term damage that results?

Awkward questions about the implications of the growing body of research have now spilled over into journalism. The sports network ESPN, which has covered the issue of athletic concussions in the past, was set to partner with PBS' Frontline program to produce a documentary called League of Denial. Then, late last week, the Frontline site released a notice saying that ESPN had suddenly pulled out of the project. Shortly after, The New York Times reported that this pull back was a product of pressure from the National Football League, which (probably rightly) feared that a documentary with that title would not put it in a positive light.

The NFL quickly issued a denial, while ESPN claimed that it simply asked that its name be removed from a project that it had little editorial control over. (In light of the public spat, ESPN's ombudsman analyzed the situation at length.)

The documentary will go on regardless of ESPN's involvement, and researchers will continue to work to define the parameters that lead to long-term damage and then (hopefully) craft those into advice on how athletes of various ages can preserve their brains. Having a major sports broadcaster amplify the message might have helped raise awareness of this issue. A public controversy like this, however, might serve equally well.