COLUMBIA Mo.

The growing number of exercise-induced deaths among athletes with sickle cell trait can be curtailed with proper treatment and greater awareness among team doctors and athletic trainers, a national medical group said in a report released Wednesday.

The National Athletic Trainers' Association report, released at the group's annual meeting in Anaheim, Calif., only suggests, not recommends, that schools screen players for the inherited blood disorder.

The symptoms of explosive muscle breakdown tied to sickle cell trait are "underrecognized and often misunderstood" by team medical workers who mistake the injury for heat exhaustion, muscle cramps or heart problems, the report found.

"Sickling collapse is a medical emergency," the report states.

Nine athletes have died under such circumstances in the past seven years, ranging in age from 12 to 19. The NATA study also notes the deaths of 13 college football players at schools that did not test for sickle cell trait or had "a lapse in precautions."

Three of those deaths occurred over the past three summers. The group includes former Missouri reserve linebacker Aaron O'Neal, who collapsed on the field near the end of a preseason workout in July 2005.

"I have no doubt that I'm very typical of a lot of sports medicine professionals," said Scott Anderson, head athletic trainer at the University of Oklahoma and a co-chairman of the NATA task force that produced the report.

"There's knowledge of sickle cell trait, but a great lack of understanding of the associated risks," he said.

In Missouri, a county medical examiner listed O'Neal's official cause of death as viral meningitis. That determination was challenged by several people, including outside experts and the chairman of the university's pathology department.

Individuals with sickle cell trait have one normal gene for hemoglobin, the protein in red blood cells, and one abnormal gene. Unlike normal, rounded red blood cells, the sickle-shaped cells carry less oxygen and can clog blood vessels that flow to the heart and other muscles.