The sport often regarded as the world's most wide-open and disorganized, boxing, is also the most regimented in its response to head injuries.
When the referee stops an amateur bout, the loser disappears from the scene for a period ranging from 30 to 180 days, according to the official rules of USA Boxing.
Passbooks containing fight histories accompany amateurs in search of competition. They can't fight without the document, which works as a monitor for knockout victims.
"It's a nice, simple system, but one that makes it relatively easy to regulate and make sure that people who have been knocked out can't get back right away," said Dr. Walter Stewart, who serves as a physician at many fights in the area.
As clear as boxing's system is on concussions, ambiguity rules elsewhere. None of the major professional sports leagues, or the NCAA, has a policy on the management of concussions that athletes suffer during competition or practices.
The NCAA issues a medical handbook that gives guidance to individual schools. The text has a section on concussions and what is known as second-impact syndrome, which involves head injury that occurs before the initial symptoms of the first injury have been resolved.
Readers of the handbook get information about concussions, post-concussion syndrome and about second-impact syndrome.
They get general guidelines -- no one rendered unconscious should be allowed to return to that day's game, nor should anyone return to competition while still suffering from symptoms of traumatic brain injury.
But the manual stops there, leaving coaches, players, athletic trainers and physicians in the gray area known as clinical judgment.
"We basically say that each team physician in the specific situation should warrant or justify when people get to play," said Randall Dick, who coordinates injury surveillance for the NCAA.
Still, two athletic trainers at local schools, Gary Horsmon of Johns Hopkins and Terry O'Brien of Towson, say that they're careful when it comes to concussions and that it's not something that needs arbitrary mandates.
"You treat every situation individually, and try to apply some objective measurement to that situation," Horsmon said. "Assessing the severity of a multitude of symptoms at any given time."
Instead, both work on a multi-grade system in which injured players may return on the same day only if they have mild symptoms, which should disappear within 15 minutes. Otherwise, players won't be able to return to action until at least a week after they've recovered their full senses, as determined by a series of tests.
Horsmon, who has seen two athletes with post-concussion syndrome at Johns Hopkins this fall, said that athletes need to be able to make responsible decisions, especially after several brain injuries.
One reason that organizations like the NCAA avoid hard-and-fast rules has been the lack of a consensus on what to do about traumatic brain injuries.
Rita Glassman of the National Youth Sports Safety Foundation in Boston said that those participating in youth sports are at risk, as a result.
"Obviously, there are a lot of turf wars on these things, and it's quite unfortunate, because children are the losers," she said. "Where there is controversy, that does not help the situation. Our hopes are that they'll adopt the most conservative ones."
O'Brien said the most conservative guidelines probably wouldn't work, as they advocate minimal participation for those who have suffered the mildest of concussions.
"A significant portion of the athletes playing at a given time would be taken out of the game," he said. "It's not a bad thing, but it's unrealistic."