NORMAN, Okla. -- Nearly four decades ago, the U.S. military confronted the dangers of an inherited condition known as sickle-cell trait. During a four-year span in the early 1970s, one Air Force cadet died and three others collapsed while participating in basic training.
A military study revealed that applicants with sickle-cell trait were 30 times more likely to die during basic training. The Air Force even went so far as to temporarily ban recruits with the condition.
About 25 year later, on the campus of the University of Oklahoma, Scott Anderson was in his first year as the school's head athletic trainer when a football player began struggling with severe back spasms on a grueling first day of conditioning. Anderson and others believed the problems were heat-related.
"It was a glorious August summer day," says Anderson.
But when the player didn't respond to treatment, he was hospitalized for testing and observation. After it was revealed the player had sickle-cell trait, the case was reviewed and it was determined that the incident was tied to the trait and overexertion.
By June of 2007, Anderson had become something of an expert in the area, working with others to educate his fellow athletic trainers and additional medical personnel about a condition they believed was tied to the deaths of nine young athletes over the previous seven years. (That number is now 11.)
The sickle-cell gene is inherited, and is most common among people whose family originated from areas where malaria is widespread, according to NATA. The result is that one in 12 African-Americans have the trait, compared to anywhere from one in 2,000 to one in 10,000 Caucasian-Americans, according to NATA.
The parents of Ereck Plancher, a University of Central Florida football player whose death in March was linked to sickle-cell trait, are from Haiti. Anderson says six players on the current Oklahoma team have the condition.
The trait is distinguished from the serious disease sickle-cell anemia in that only one sickle-cell gene is present with someone who has the trait, and two are present in someone with sickle-cell anemia.
"It is certainly not a limit on athletic participation," Anderson says of athletes with the trait. "It certainly doesn't mean one can't achieve elite levels of athletic participation. That has been proven over and over again by a number of individuals."
However, the NATA committee, citing the military studies and additional case studies, warned in June 2007 of potentially severe consequences for sickle-cell athletes who overexert themselves, particularly during the first day of conditioning sessions. Plancher died on the first day of Central Florida's offseason conditioning sessions after spring break.
In an athlete with the trait, red blood cells can change shape during intense training. The result is sickle-shaped cells that can become logjammed in blood vessels and prevent the body from getting necessary oxygen.
"When the cells change shape, then they can't flow as well," says Oklahoma head team physician Dr. Brock Schnebel. "When they can't flow as well, then that causes problems with circulation."
Schnebel says there are four exercise-related factors that can contribute to the onset of sickle-cell collapse: oxygen levels dropping from exertion, high body temperature, dehydration and lowering of pH levels in the bloodstream.
The NATA report and an accompanying press release issued in the summer of 2007 said that "education" and "simple precautions may prevent sickling collapse and enable athletes with sickle cell trait to thrive in sport."
Anderson says screening for sickle-cell trait is a simple and relatively cheap endeavor: $5 for the initial screen, $30 to confirm a positive, for a total of $35 -- the same price, the trainer notes, as a pair of Nike receiver gloves. The NCAA leaves it to individual schools to decide whether to screen for the trait, and there is no data on how many schools perform screening. It has been a constant at Oklahoma for more than a decade, Anderson says. At UCF, Plancher had been screened for the trait, and the school said coaches, trainers and Plancher himself were aware he had the condition.
The NATA committee's statement recommended a series of basic precautions for preventing sickling collapse. Among the suggestions were extended rest for the athletes and a gradual progression of workouts, as well as a reminder that several deaths had occurred during the first day of training.
"One can easily look at this and say, 'Here's a population being singled out,'" Anderson says. "But we consistently single out individuals for modifications. We modify workouts if someone has a shoulder injury. We modify workouts if someone has a knee injury. Within a population of 100-plus football players, there's gonna be various accommodations."
The NATA statement warned that "sickling can quickly increase to grave levels if the stricken athlete struggles on or is urged on by the coach."
Not that conflicts don't arise in trying to find the balance between coaches pushing players -- or players pushing themselves -- and taking appropriate precautions.
"That is one of the age-old struggles between sport and sports medicine," Anderson says. "We know and understand that our coaches haven't achieved the level of success they have by essentially taking 'no' for an answer, and that everybody that's been involved in sport has been pushed, and pushed themselves maybe, beyond their limit."
Anderson and Schnebel say players, too, must be prepared to advocate for themselves, informing trainers and coaches when they are showing symptoms that could be tied to sickle-cell trait.
Even with education and precautions, Schnebel says the problem won't be completely eliminated.
"I think we can help," he says. "I think screening helps. I think doing the precautions helps. But I still think it will be a problem as long as we have athletes pushing themselves hard."
Mark Fainaru-Wada is a reporter for ESPN's enterprise unit. He can be reached at email@example.com.