Understanding Heat Exhaustion

Health Check

Understanding heat exhaustion is important since several hundred runners each summer suffer heat stroke or collapse from heat exhaustion. This occurs when a runner or other individual is unable to regulate his or her body temperature. It is important for everyone who exercises in hot, humid temperatures to understand how their body responds to these temperature. Furthermore, the same individuals need to know how to help to regulate their own temperature.

Maintaining your body’s core temperature at desirable levels, (up to 105 degrees F during exercise) is essential to prevent the detrimental effects of heat generated from exercise. A rise in your body’s core temperature mostly results from the intensity of exercise over a given period. With time, discontinuing the exercise will lower core body temperature. Heat from outside temperature has less effect on directly increasing core body temperature. However, hot humid temperatures make it very difficult for the body’s normal cooling processes to perform their functions.

The body attempts to cool itself during prolonged exercise by increasing the blood flow to the skin while transporting internal heat to the skin in the blood. We then release fluid from the body in the form of sweat when our skin pores dilate. The sweat carries the heat outside of the skin where it evaporates into the air. Every liter of sweat that evaporates accounts for 580 kilocalories of heat energy removed from the body.

In hot, humid temperatures, the evaporation of sweat is difficult due to moisture levels in the air. However, after as little as four to 14 days of training in the heat you can develop increased capabilities to exercise in hot conditions. A principal adaptation the body undergoes when becoming acclimated to exercising in the heat is that our sweat glands dilate more thus allowing us to sweat more rapidly and more profusely. This diluted sweat more easily evaporates into the air.

Understanding Heat Exhaustion – Treating This Condition

To allow for increases in sweat production, we must maintain adequate levels of hydration in our body. We recommend the following guidelines for fluid consumption in the heat:

– Individuals should consume approximately 20 oz. of cold water (50 degrees F) 20 to 30 minutes before exercise. Sports drinks that contain too much salt or sugar will retard the absorption of the water into the body.

– Drink four to eight ounces of cold water every 15 minutes during exercise. The cold temperature of the water can actually help reduce core body temperature while exercising.

– Prevent dehydration by recording body weight daily to monitor fluid loss. If not regained within 36 hours of exercise, the athlete should consume more fluid even if it creates a bloated sensation.

– Replenish salt lost from exercise after the exercise either by salting your food moderately or consuming sports drinks with electrolyte supplements. Sodium is the most important electrolyte that must be replenished. Electrolyte replacement without adequate replenishment of water may increase dehydration which will adversely affect performance.

Individuals who experience extreme fatigue, dizziness, muscle cramping and/or lack of ability to maintain athletic performance may be experiencing forms of heat exhaustion. They should discontinue their exercise, rest in a cool place and drink cool water.

Please refer to patient education for other brief articles in our educational series. It is through these articles, in part, that we keep our patients (and others) informed of common injuries and conditions, their treatment and healthcare in general.