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Heat stress injuries are preventable — here's how

After more than a dozen high school football players were hospitalized last week in McMinnville, Ore., news reports blamed a "mystery" illness. Emerging details suggest a not-so-mysterious cause: heat stress injury as a result of vigorous training in hot weather at the start of the season when athletes aren't fully conditioned.

Such factors set the stage for about 9,200 heat-stress injuries a year in the United States, according to Ohio State University researchers. Football players accounted for more than 70 percent of cases from 2005 to 2009.

Heat exhaustion and heat stroke are the most well known consequences. Since 1995, 31 high school football players have died from heat stroke, the Centers for Disease Control and Prevention reported last week.

But intense physical exertion can cause a muscle-damaging syndrome called rhabdomyolysis, the problem in McMinnville. Over-taxed muscle fibers break down and release protein into the bloodstream at levels toxic to the kidneys. It can cause life-threatening kidney failure or sudden cardiac arrest from severe electrolyte imbalance in young, healthy athletes.

Exercise-induced rhabdomyolysis can lead to excruciatingly painful — and potentially crippling — compartment syndrome, as it did in several McMinnville players. Fluid pressure rises to a critical level inside the fascia that enclose limb muscles in sealed compartments. Car accidents and other traumatic injuries are the most common cause of compartment syndrome. World War II doctors were among the first to recognize exercise induced compartment syndrome, calling it "march gangrene." At least 10 reports of athletes developing compartment syndrome after heavy exercise have appeared in medical journals since 2001.

Experts say practically all heat stress injuries among athletes could be prevented.

"Football training and play can be done safely even in hot conditions — if you do it appropriately," says Michael F. Bergeron, director of the National Institute for Athletic Health and Performance in Sioux Falls, S.D. "Coaches put players at risk by trying to do too much, for too long, too soon."

To prevent heat stress injuries, experts convened by the American College of Sports Medicine highlight these key steps:

Take time to adjust: Two-thirds of heat-stress injuries among high school athletes occur in August, often during the first few days of practice when it's hottest and athletes are least fit. That's why it's pivotal for coaches to gradually raise training intensity. Athletes need time to adapt to hotter weather, to longer or more-intense workouts, and to the added heat stress of helmets and pads

Pay attention to temperature and humidity: When weather turns hotter or more humid, athletes and coaches should dial back the intensity of training and take longer and more frequent breaks to allow the body to dissipate heat.

Stay hydrated: Working out in hot weather, an athlete's body can quickly lose more than 5 percent of body weight in water. That much dehydration undermines sweat production and blood flow to the skin, making it harder for the body to dissipate heat. Athletes should develop individualized fluid replacement plans to avoid losing more than 2 percent of body weight from dehydration. One way to do that is to weigh--in before and after workouts.

"For every pound down, you need to drink about 16 to 20 ounces of fluid over course of the following afternoon and evening," Bergeron says.

Urine color is another guide: Dark indicates dehydration, colorless suggests you are drinking too much, lightly colored is ideal.

Actively monitor athletes: In hot weather and at early-season training, coaches need to look for signs and symptoms of heat illness and dehydration, and encourage athletes to watch each other. Symptoms such as dizziness, unusual behavior, headache, loss of balance, profound fatigue, hyperventilation and vomiting could indicate life-threatening heat stroke and the need for urgent medical attention. Bergeron says coaches and trainers should be ready to rapidly cool athletes suspected to have heat stroke. Preparation could be as simple as keeping a wading pool ready with water and ice.

Copyright © 2015, The Baltimore Sun
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