Heat-related illness continues to be a significant threat to athletic performance and overall health. Among high school athletes heat-related illness is the third most common cause of death. In order for the body to function normally, its core temperature must remain within a narrow range around 98.6°F (37.0°C). Acclimating to warm outdoor temperatures means that the body makes adjustments so that you do not feel the adverse effects of heat. The primary way the body acclimates is by sweating. The process of sweating helps cool the body, but it also results in the loss of water and electrolytes (e.g. sodium, chloride). Electrolytes are substances that help the body maintain fluid balance. Dehydration is the excessive loss of fluid and electrolytes from the body, and it leads to heat-related illness. Replacing lost water and electrolytes by drinking fluids is essential to maintaining normal core temperature and bodily functions. Therefore, athletes need to drink fluids to avoid heat-related illness.
The point at which the body starts to sweat in response to heat is higher in children than adults. Children also sweat at a slower rate than adults. Both of these factors place children at higher risk for developing heat-related illness. Other risk factors for heat-related illness include under-hydration, obesity, poor fitness, sleep deprivation, and illness that impairs the body’s ability to sweat. Athletes with heat-related illness may experience profuse sweating, muscle cramps, dry mouth, low urine output, fatigue, headache, nausea, and a change in mental status (dizziness, fainting). Overall, the basic treatment for athletes experiencing these symptoms is to stop playing, move to a cooler area, drink fluids, and seek evaluation by a doctor.
The key steps to prevent heat-related illness are drinking fluid to replenish water and electrolytes and avoiding overexertion in warm climates. By the time an athlete is thirsty, dehydration may already be developing. Therefore, thirst is not a reliable indicator of fluid replacement needs during athletic activity. Ideally, replacement of fluid should be equal to the amount of sweat an athlete produces per hour during activity (hourly sweat rate).
Athletes should be encouraged to drink before, during, and after activity to replenish fluids and electrolytes and to prevent dehydration before it starts to develop. However, drinking an excessive amount of fluid can be harmful to the body and is not recommended. Overall, fluids (water, sports drinks) should be consumed at levels approximately equivalent to sweat lost during activity as determined by the hourly sweat rate. The guidelines for fluid replacement established by American College of Sports Medicine should be reviewed by all athletes, coaches, and parents. Heat-related illness is largely preventable with careful attention to the temperature, hydration, and activity level.
Resources for more information on heat-illness see the position statements developed by the American College of Sports Medicine:
- Exertional Heat-Illness During Training & Competition www.acsm.org
- Exercise & Fluid Replacement www.acsm.org