Bright Futures in Practice: Physical Activity

HEAT-RELATED ILLNESS

Heat-related illness occurs when the body gets overheated. Heat and humidity affect the body's ability to dissipate heat. When temperature and humidity levels are high, less sweat evaporates from the skin, making it more difficult for the body to cool itself. Children and adolescents who are physically active in extreme heat and humidity are at risk for heat-related illness.

Significance

Children and prepubertal adolescents develop heat-related illness more easily than older adolescents and adults because they

Have a lower sweating rate (absolute and per sweat gland), which can decrease the body's capacity to dissipate heat.
Produce more heat when they are physically active, and are less able to transfer heat from the muscles to the skin.
Have a larger body surface area relative to their weight, which can result in excessive heat gain in extreme heat.
Have lower cardiac output, which reduces their capacity to transfer heat from the body core to the skin during vigorous physical activity.
Take longer to acclimatize to physical activity in hot weather. A child or prepubertal adolescent may need to participate in five or six sessions of an activity to achieve the same degree of acclimatization acquired by an adult during two or three sessions of the same activity in the same environment.

Heat-Related Illness and Chronic Conditions and Disease

Children and adolescents with a chronic condition or disease, as well as those taking certain prescription or over-the-counter medications, are at higher risk for heat-related illness. Those with bulimia nervosa, congenital heart disease, diabetes mellitus, gastroenteritis, obesity, or a fever may experience excessive fluid loss. Those with anorexia nervosa, kidney disease, cystic fibrosis, or mental disability may not consume enough fluids because they refuse or are unable to drink enough and/or because their bodies need additional fluids as a result of their condition.

Children and adolescents who have a chronic condition or disease, and who are thus at higher risk for developing heat-related illness, should be watched closely when they are physically active. However, under most circumstances, they can safely participate in physical activity. In addition, physical activity can help these children and adolescents improve their general health status.

Prevention

To prevent heat-related illness, children and adolescents must maintain hydration by replacing fluid that is lost during physical activity. In addition, parents, physical education teachers, coaches, and health professionals need to be aware of the signs, symptoms, and treatment of heat-related illness (Table 22).

One way to prevent heat-related illness is by determining whether it is safe for children and adolescents to participate in physical activity outdoors (Figure 3). Even though the table was developed specifically for football, it can also be used to determine the safety of participating in other physical activities outdoors. Parents, physical education teachers, and coaches can plot the temperature on the horizontal axis and the humidity on the vertical axis. The intersection of the two axes indicates whether it is safe to be physically active outdoors. Zone 1 (safe) indicates that it is safe; zone 2 (use caution) indicates that children and adolescents at high risk for heat-related illness should be watched carefully for symptoms of heat-related illness; and zone 3 (use extreme caution) indicates that it is dangerous to be physically active outdoors.

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