Hydration and Prevention of Heat Illness
The following post references the practices I recommended during my tenure as the Head Athletic Trainer at the University of South Carolina. The University is in the midst of the heat belt of southeastern United States, and aggressive strategies had to be embraced to keep our student-athletes safe.
Heat illness is a condition of concern to those exercising in the extremes of weather—especially during the summer months. Heat is produced as a by-product of exercise. Thus, coaches and athletic trainers must be aware of the potential for heat related illness in all environments and conditions—not just during the pre-season football practice. The evaporation of sweat is the primary way the body loses heat and regulates a safe body temperature. Thirst is not a good indicator of a person’s fluid needs. By the time you’re thirsty, you have already lost fluids and may be dehydrated. Coaches and athletic trainers must utilize strategies to monitor weight (fluid) loss and make sure dehydration is avoided, especially when exercising in warm weather.
Muscle energy produces heat from muscle contractions and metabolism. The main way to reduce body temperature is from sweating. When sweat evaporates from your body, heat is lost and so are body fluids. You need to replace those fluids to avoid dehydration and to maintain your performance. We monitor player’s weight by requiring weigh-in prior to and following each practice. Thus, our physicians and athletic trainers can monitor weight loss and make sure vital fluids are replaced prior to subsequent activity.
During exercise, heat is lost by four ways: radiation, evaporation, conduction and convection. With radiation, heat radiates from the body to cooler objects. Conduction occurs as heat is transferred from the body by direct physical contact (i.e., skin immersed in cool water; person swimming in cool water). The transfer of heat by movement of cool currents of air or water over the body describes convective cooling. The conversion of sweat to water vapor and movement from the skin describes cooling via evaporation.
With athletes, we want to be aware of evaporation and radiation as effective cooling mechanisms. Radiation is generally effective in temperature less than 85o F. and evaporation effective in environments with less than 70% relative humidity. It is important that coaches and athletic trainers monitor the weather and make appropriate changes in practice schedules if temperatures approach such ranges. A good reference for Heat Index Chart is the National Oceanic and Atmospheric Administration (www.gssi.com).
The following are points our physicians and athletic trainers recommend to our student-athletes. As an institution using Gatorade products, we communicate the following information to our coaches to protect our athletes in hot seasons.
• Allow for acclimatization (adaptation) in hot seasons. Cut back on exercise intensity and duration in hot weather. Slowly build back to previous level over the next 10 days.
• Drink up when it’s hot. Once acclimatized, sweat losses will be higher, so fluid intake has to be greater. We monitor weights daily and encourage copious intake of Gatorade.
• Don’t be overly competitive under hot conditions. Try for a personal best on a cooler day. Monitor weather and adjust practice schedules – workouts accordingly.
• Don’t just pour water over your head. It may feel great, but it won’t help at all at restoring body fluids or lowering body temperature. Fluid has to go in the body. Again, monitor weight loss via weight charts and replace fluids.
• Carry sports drinks, like Gatorade, with you if you know they will not be available at the exercise site. Bottle belts are great for this. Also carry money to buy something to drink.
• Select lightly flavored, sweetened beverages containing sodium. Sodium has been scientifically proven to encourage voluntary drinking and promote hydration. You can—and will drink more Gatorade than water. Research and pilot studies are showing encouraging results in the utilization of sodium to facilitate fluid intake.
• Exercise in the morning or evening when the weather is coolest. Avoid the sun’s rays to minimize the radiant heat load. However, if team practice sessions will be in the heat of the day, you need to condition your body to be acclimatized for the heat and humidity stresses of practice time.
• Wear light-colored, lightweight porous clothing. Do not change into a dry shirt at breaks or time-outs. Completely soaked shirts do better at cooling the body.
• Gatorade contains electrolytes (sodium, chloride, and potassium) to drive fluid consumption and replace minerals the body loses in sweat. It is a 6% carbohydrate solution (14 grams of carbohydrate per 8-oz serving), proven to be the optimal amount to speed hydration and assure rapid energy delivery to the body. Gatroade has a palatable flavor (light, slightly sweet flavor system) designed to taste good when an athlete is hot and sweaty.
• Water is an essential fluid, however contains no electrolytes, carbohydrate or flavor benefits. As a result, athletes will not drink enough water to maintain fluid balance. Drinking too much water can also cause an athlete to become hyponatremic (dangerously low levels of sodium in the blood) that can impair an athlete’s performance and prove perilous to health.
For more information, refer to www.gssi.com.
Tags: heat exhaustion, heat stroke, prevention, weight charts