All athletes should be properly hydrated before they start any exercise session, according to a NATA statement, and all fluids should be replenished within no more than two hours after the exercise is completed. If signs of dehydration do appear, athletes should be moved to a cool environment and rehydrated, the NATA experts advise.

Strenuous physical activity coupled with environmental heat stress can also lead to heat stroke, which is characterized by abnormalities in the central nervous system, or heat exhaustion, which describes the heart's inability to maintain a normal output. In both cases, an athlete may experience headache or dizziness. Those suffering from heat stroke may also be affected by seizures, confusion or other dysfunctions of the central nervous system, while athletes with heat exhaustion may lose coordination, sweat profusely, or experience stomach or intestinal cramps.

The best treatment for exertional heat stroke is whole-body cooling, such as immediate immersion in cold water, according to the NATA statement. Athletes with heat exhaustion should be cooled in an air-conditioned area, lying down with their legs propped above their heart level, while undergoing heart rate, blood pressure and other medical monitoring.

Athletes may also experience heat cramps while performing intense exercise in the heat. This condition often occurs in ice hockey players also, however, the NATA experts note. Heat cramps may be alleviated once athletes are rehydrated and they consume sports drinks or other fluids to replace the sodium lost during exercise.

Excessively low sodium levels, which can occur when an individual is overhydrated, may ultimately result in fluid accumulating in the brain and/or lungs. Signs and symptoms include nausea, vomiting and swelling of hands and feet. In this situation, transportation to a medical facility may be the best course, so that sodium can be measured and adjusted as need.

To prevent such problems, NATA recommends that medical services be provided onsite at various sporting events and that athletes complete physical examinations, including specific questions about their history of heat illnesses and fluid intake, before participating in sports.

NATA also recommends that medical staff be given the authority to change athletes' practice schedules and their amount of equipment, based on the day's heat and the athlete's medical conditions.

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