As football season heats up, so will the thousands of players hitting the field for practice. But the problem, researchers say, isn't the players' performance -- it's their body temperatures.
Heat acclimation, or training the body to better adapt to heat during exercise, has found its way into the NCAA's regulations for football players. At present, teams are required to hold less intense practices once per day for seven to 10 days in the heat before transitioning into more intense schedules with more than one practice per day.
But how does the process actually work?
Christopher Minson, associate professor and head of the University of Oregon department of physiology, told Discovery News that in order to understand heat acclimation, one should first tackle thermoregulation, or how the body cools itself. Blood usually carries heat away from active muscles to the surface of the skin, where sweating takes over.
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"A high skin blood flow takes warm blood from our working muscles where metabolism is occurring and brings it to the surface of the body where then evaporation (through sweating) allows that heat to transfer to the environment," Minson said. "Sweat on your skin has to go from a liquid form to a gaseous form, and it takes energy to make that shift -- (also) called latent heat of evaporation."
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Problems arise when football players wear clothing or equipment that hinders their ability to dissipate heat. Humidity plays a large role, too, since it doesn't allow sweat to evaporate.
Football athletes are at higher risk of overheating, especially in humid regions of the country and during high temperatures in August, when approximately 96 percent of heat illnesses occur, according to the NCAA.
In humid conditions or when players aren't acclimated, they're unable to dissipate heat through sweat. As a result, their core body temperatures can rise to dangerous levels that damage the brain and can even be fatal.
To avoid unsafe practicing conditions, Minson said coaches and athletic trainers -- both at the collegiate and high school levels -- need to monitor wet bulb globe temperatures, which include temperature, humidity and solar radiation.
But heat acclimation is still a primary method to prepare athletes for the heat.
"One of the primary things that happens with heat acclimation is we increase the water -- the plasma -- in our blood," Minson said. "The plasma is very important because if you maintain your blood volume, then your heart works better to move heat to dissipate at the skin. It also works better to get blood to working muscles."
Essentially, heat acclimation decreases the effects of dehydration on the body -- a primary risk factor for heat illnesses. In addition, molecules called heat shock proteins increase during the heat acclimation process. These "molecular chaperones," if you will, keep tissues stable and also influence other areas of the body and brain, he said.
The best approach, Minson said, is beginning heat acclimation after a person is already in shape.
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Though heat acclimation isn't new, one researcher said states have failed to create science-based rules to protect high school players. Douglas Casa, chief operating officer at the Korey Stringer Institute at the University of Connecticut, told Discovery News that all teams should have a sports medicine expert on hand. The institute was founded after Stringer, a Minnesota Vikings offensive lineman, died of heat stroke in 2001.
Casa and his colleagues have helped establish guidelines for the NFL, NCAA and some states' high school football programs, but he said it's tough to deal with 50 states and multiple entities within each.
"It's a full-time job just to get a couple of states to make changes," Casa said. "The policies need to come from experts on the topics of heat illness and sports medicine, and not from football people. They need to look at what's best for the athletes."
Though Casa said states such as New Jersey and Arkansas have stepped up to the plate, he would like to see more create policies proactively instead of as a reaction to teen deaths. He said the NCAA serves as an excellent example of how acclimation protects players. Since the organization created its heat acclimation regulations in 2003, only one death has occurred in the month of August in comparison to one to two in the same month in previous years.
So far, six deaths have occurred at the high school level this August alone.
It's also important for trainers, coaches and players to know the signs of heat illnesses, including sudden weakness, abrupt changes in sweating, cramping, nausea, blurry vision and delayed cognition. Heat exhaustion can often be treated on the field, whereas heat stroke requires immediate medical attention, Casa said. Being overweight or not acclimated to the heat are major risk factors.