Pioneer Valley Youth Sports and Fitness Institute

the source for sound athletic advice

Table 1. Major Risk Factors for Heat Stroke

Environment                    Physical Activity             Age

High temperature               Vigorous exercise             Older than 75

High humidity                    Heavy exertion                  Younger than 5

Little or no wind                 Intense activities      

Other Risk Factors for Heat Stroke

Male gender                 Lack of acclimatization              Lack of fitness

Previous heat stroke     Wearing excessive clothing       Obesity

Dehydration                  Fatigue                                    Illness/Disease

Malnutrition                  Alcohol use                              Certain medication

Table provided by Joseph Warpeha, MA, CSCS,*D

Heat Stroke and Exercise

New England this time of year is perfect in my mind. The temperature is warm, humidity is relatively low, and spring allergies have past by.  Soon things will change, the temperature will be hot and humidity high.  It is during that period of time when the most severe of all heat illnesses occur, heat stroke. Heat stroke is the most frequent environmentally-related cause of death in the U.S. with about 400 deaths per year attributed, according to TP Moreau.  Heat stroke is the second only to head injuries in exercise-related deaths and the third leading cause of death among athletes in the U.S.

Simply put, heat stroke occurs when our internal thermostat that keeps our body temperature in a somewhat narrow operating range “breaks down” resulting in a rise of the body’s core temperature, if appropriate measures are not taken quickly this event can become fatal.

There are two classifications of heat stroke, classical or exertional. Classical heat stroke is diagnosed by criteria including central nervous system dysfunction (e.g. confusion, unconsciousness), hot dry skin, and core temperature >41°C. The only significant criteria difference for exertional heat stroke is the core temperature may be slightly lower and profuse sweating is usually present. Other symptoms present include rapid heart beat, rapid and shallow breathing, altered blood pressure, altered mental status, vomiting, and diarrhea.

The major risk factors for heat stroke are environment, physical activity and age. See table 1 for at stroke risk factors.

Since the hot environment is the main risk factor, it is important to have a familiar way to identify how hot it “feels”, use of the heat index which factors temperature and humidity. The heat index is easily accessible to the public via the news media such as television, radio, internet, and newspapers.

The best way to avoid heat stroke is precaution. The most ideal precaution is to adhere to heat warnings in news media and avoid exercise in dangerously hot conditions.  Limit direct sun exposure to reduce radiant heat and its influence on the heat index.  Maintaining appropriate hydration levels and salt/electrolyte stores during prolonged exercise is of the utmost importance.  Athletes and exercisers need to acclimatize themselves to hot conditions over several days or weeks allowing adaptive mechanisms to take place in order for the internal thermostat to function more efficiently.

The human body is amazing in its ability to adapt to environmental extremes, the body does have its limits however.  During the dog days of summer, whether you are and outdoor fitness enthusiast or athlete performing conditioning drills outside adhere to weather warnings and use precautionary methods to avoid heat stroke and other related heat illnesses.

Len Haggerty owns and operates STRIDES Performance & Wellness in Northampton, MA. He encourages youths, competitive and recreational athletes, and adults to discover their athletic potential. Len can be contacted at len@strideshpi.net to address any questions.