Heat Stress and Athletic Participation
Early fall football, cross country, soccer and field hockey practices are conducted in very hot and humid weather in many parts of the United States. Due to the equipment and uniform needed in football, most of the heat problems have been associated with football. During hot weather conditions, the athlete is subject to the following:
- Heat Cramps - Painful cramps involving abdominal muscles and extremities caused by intense, prolonged exercise in the heat and depletion of salt and water due to sweating.
- Heat Syncope - Weakness, fatigue and fainting due to loss of salt and water in sweat and exercise in the heat. Predisposes to heatstroke.
- Heat Exhaustion (Water Depletion) - Excessive weight loss, reduced sweating, elevated skin and core body temperature, excessive thirst, weakness, headache and sometimes unconsciousness.
- Heat Exhaustion (Salt Depletion) - Exhaustion, nausea, vomiting, muscle cramps, and dizziness due to profuse sweating and inadequate replacement of body salts.
- Heatstroke - An acute medical emergency related to thermoregulatory failure. Associated with nausea, seizures, disorientation, and possible unconsciousness or coma. It may occur suddenly without being preceded by any other clinical signs. The individual is usually unconscious with a high body temperature and a hot dry skin (heatstroke victims, contrary to popular belief, may sweat profusely).
It is believed that the above mentioned heat stress problems can be controlled provided certain precautions are taken. The following practices and precautions are recommended:
- Each athlete must have a physical exam with a medical history when first entering a program and an annual health history update. History of previous heat illness and type of training activities before organized practice begins should be included. State high school association's recommendations should be followed.
- It is clear that top physical performance can only be achieved by an athlete who is in top physical condition. Lack of physical fitness impairs the performance of an athlete who participates in high temperatures. Coaches should know the physical condition of their athletes and set practice schedules accordingly.
- Along with physical conditioning, the factor of acclimatization to heat is important. Acclimatization is the process of becoming adjusted to heat and it is essential to provide for gradual acclimatization to hot weather. It is necessary for an athlete to exercise in the heat if he/she is to become acclimatized to it. It is suggested that a graduated physical conditioning program be used and that 80 percent acclimatization can be expected to occur after the first seven to ten days. Final stages of acclimatization to heat are marked by increased sweating and reduced salt concentration in the sweat.
- The old idea that water should be withheld from athletes during workouts has no scientific foundation. The most important safeguard to the health of the athlete is the replacement of water. Water must be on the field and readily available to the athletes at all times. It is recommended that a minimum of ten minutes be scheduled for a water break every half hour of heavy exercise in the heat. Water should be available in unlimited quantities. Check and be sure athletes are drinking the water. Cold water is preferable. Drinking ample water before practice or games has also been found to aid performance in the heat.
- Salt should be replaced daily. Modest salting of foods after practice or games will accomplish this purpose. Salt tablets are not recommended. Attention must be directed to replacing water - fluid replacement is essential.
- Know both the temperature and humidity. The greater the humidity, the more difficult it is for the body to cool itself. Test the air prior to practice or game using a wet bulb, globe, temperature (WBGT) index which is based on the combined effects of air temperature, relative humidity, radiant heat and air movement. A WBGT device is a measurement tool that uses ambient temperature, relative humidity, wind, and solar radiation from the sun to get a measure that can be used to monitor environmental conditions during exercise. Establishing WBGT guidelines that dictate modifications in activity (work:rest ratios, hydration breaks, equipment worn, length of practice) at given WBGT temperatures play a huge factor in helping to prevent EHS. Readings should be taken before and during every outside event or practice to accommodate accordingly based on adopted guidelines. The map and table to follow provides a guideline for modification of activity based on the environmental conditions in each region. source: Grundstein et al. Regional heat safety thresholds for athletes in the contiguous United States. Appl. Geography. 2015.pdf
- Cooling by evaporation is proportional to the area of skin exposed. In extremely hot and humid weather reduce the amount of clothing covering the body as much as possible. Never use rubberized clothing.
- Athletes should weigh each day before and after practice and weight charts checked. Generally a three percent weight loss through sweating is considered safe and over a three percent weight loss is in the danger zone. Over a three percent weight loss the athlete should not be allowed to practice in hot and humid conditions. Observe the athletes closely under all conditions. Do not allow athletes to practice until they have adequately replaced their weight.
- Observe athletes carefully for signs of trouble, particularly athletes who lose significant weight, and the eager athlete who constantly competes at his/her capacity. Some trouble signs are nausea, incoherence, fatigue, weakness, vomiting, cramps, weak rapid pulse, visual disturbance, and unsteadiness.
- Teams that encounter hot weather during the season through travel or following an unseasonable cool period should be physically fit but will not be environmentally fit. Coaches in this situation should follow the above recommendations and substitute more frequently during games.
- Know what to do in case of emergency and have your emergency plans written with copies to all your staff. Be familiar with immediate first aid practices and prearranged procedures for obtaining medical care, including ambulance service
Heat Stroke - This is a medical emergency. ANY DELAY COULD BE FATAL.
- Follow these steps to initiate emergency treatment (source: KSI):
- Remove all equipment and excess clothing.
- Cool the athlete as quickly as possible within 30 minutes via whole body ice water immersion (place them in a tub/stock tank with ice and water approximately 35-58¬∞F); stir water and add ice throughout cooling process.
- If immersion is not possible (no tub or no water supply), take athlete to a shaded, cool area and use rotating cold, wet towels to cover as much of the body surface as possible.
- Maintain airway, breathing and circulation.
- After cooling has been initiated, activate emergency medical system by calling 911.
- Monitor vital signs such as rectal temperature, heart rate, respiratory rate, blood pressure, monitor CNS status.
- If rectal temperature is not available, DO NOT USE AN ALTERNATE METHOD (oral, tympanic, axillary, forehead sticker, etc.). These devices are not accurate and should never be used to assess an athlete exercising in the heat.
- Cease cooling when rectal temperature reaches 101-102¬∞F (38.3-38.9¬∞C).
- Exertional heat stroke has had a 100% survival rate when immediate cooling (via cold water immersion or aggressive whole body cold water dousing) was initiated within 10 minutes of collapse
Heat Exhaustion - OBTAIN MEDICAL CARE AT ONCE. Cool body as you would for heat stroke while waiting for transfer to hospital. Give fluids if athlete is able to swallow and is conscious.
Summary - The main problem associated with exercising in the hot weather is water loss through sweating. Water loss is best replaced by allowing the athlete unrestricted access to water. Water breaks two or three times per hour are better than one break an hour. Probably the best method is to have water available at all times and to allow the athlete to drink water whenever he/she needs it. Never restrict the amount of water an athlete drinks, and be sure the athletes are drinking the water. The small amount of salt lost in sweat is adequately replaced by salting food at meals. Talk to your medical personnel concerning emergency treatment plans.