High school football players hit hard by heat

CDC. MMWR. 2010; 59:1009-1013.

Between 2005 and 2009, high school athletes lost more than 9,000 days of practice and competition per year to heat illness, with most heat-related illnesses occurring during football practice, CDC researchers reported today.

The researchers evaluated data from the National High School Sports-Related Injury Surveillance Study, which involved 100 randomly selected schools across the United States.

Nine sports were monitored: football, wrestling, soccer, baseball and basketball for boys, and volleyball, soccer, basketball and softball for girls. Weekly reports on heat illness were submitted to the researchers by National Athletic Trainers’ Association (NATA)-affiliated certified athletic trainers.

The researchers defined time-loss heat illness as dehydration or heat exhaustion/heat stroke that occurred during participation in a school sport; was evaluated by a medical professional; and caused an athlete to miss at least 1 day of practice or competition.

There were 118 time-loss heat illnesses — occurring at an average of 29.5 per school year — during 2005 to 2009 among the sports and schools, according to the researchers. The national estimated annual average of heat illnesses was 9,237 (95% CI, 8,357-10,116).

Football players experienced an estimated annual average of 6,529 heat illnesses (95% CI, 5,794-7,264). These numbers equated to an incidence rate of 4.5 heat illnesses per 100,000 in this population. This proportion is 10 times higher than the average rate for the other eight sports, the researchers said.

The rate of heat illnesses resulting from football practice was on par with that experienced during competition. The researchers noted, however, that 83.6% of all football time-loss heat illnesses occurred during practice, although this may be related to the fact that practice consumes more time than competition.

The majority of affected football players were considered overweight (37.1%) or obese (27.6%).

Most heat illnesses occurred during August when schools begin preseason training.

“Acclimatization is particularly important during preseason football practices, which typically occur during the hottest and most humid period of summer and when participants are least physically fit,” wrote the researchers. “Current NATA recommendations suggest implementation of a 14-day acclimatization period for all warm weather conditioning, with practice frequency, duration, and intensity as well as protective equipment usage increased gradually.”

NATA also recommends fluid replacement that approximately equals sweat and urine loss, as no athlete should lose more than 2% body weight per day. The researchers noted that this equates to consumption of about 200 mL to 300 mL of fluid every 10 to 20 minutes during exercise.

Coaches and athletic trainers should stress the importance of staying hydrated and thoroughly explain the dangers and signs of heat illness.

“One death due to heat-related illness is too many,” Michael McGeehin, PhD, director of CDC’s division of environmental hazards and health effects said in a press release. “Heat-related illness is preventable; the more we know about how and when it happens, the better we can prepare people who may be most at risk.”

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