Keeping Sports Participants Safe in Hot Weather
August 1, 1999 3 minutes read
Keeping Sports Participants Safe in Hot Weather
Abstract & Commentary
Synopsis: Adequate hydration must be maintained in the heat, and hyperhydration before exercise is a way of getting ahead of the curve.
Source: Sparling PB, Millard-Stafford M. Keeping sports participants safe in hot weather. Phys Sports Med 1999; 27:27-34.
Sparling and millard-stafford present a nice overview of the current thinking with regard to the prevention of hot-weather-related problems in athletics. They focus primarily upon the concept of heat dissipation and identify specific strategies for heat acclimatization and fluid replacement designed to prevent serious heat-related complications of athletic participation. The review emphasizes that athletes require almost two weeks to acclimatize to severe heat although 75% of the adaptation usually can be accomplished within the first five days. Sparling and Millard-Stafford emphasize the importance of short and less intense initial training sessions, gradually progressing to more robust workouts. They point out that chronic dehydration retards acclimatization but also emphasize the point that hyperthermia can occur even without dehydration when the exercise activity is particularly intense.
Sparling and Millard-Stafford focus on the importance of maintaining adequate hydration in the heat, citing studies showing that fluid losses, from sweating alone, in intense heat can reach as much as 300 mL every 15 minutes. They promote the concept of hyperhydration before exercise as a way of getting ahead of the curve and then recommend ingestion of about a liter per hour of fluid to maintain hydration in a vigorously active athlete.
A summary is presented on the types of rehydration drinks available on the market and the article emphasizes that electrolyte sports drinks with 5-8% carbohydrates are well tolerated by the vigorously active athlete and also seem to improve endurance.
As an interesting sidebar to the article, the effects of the hot weather environment during the 1996 Olympic games held in Atlanta, Georgia, are presented. Interestingly, the people most commonly seeking medical help for heat illness were spectators and volunteers and not the athletes, as the athletes were well acclimatized and prepared for participation. The organizers focused heavily on the measurement and interpretation of environmental heat stress using the Wet-Bulb Globe Temperature Measurements. Using these data, they were able to recommend when the athletes should and should not work out. Both marathons were begun early in the morning, specifically to avoid the high heat and humidity occurring later in the day. Endurance performances in such events as the 10-kilometer walk, the women’s marathon, and both the men’s and women’s 10-kilometer races were at world-record levels despite the heat.
Comment by James D. Heckman, MD
Sparling and Millard-Stafford present a nice overview of the important principles to be used in the prevention of heat illness in the high-performance athlete. They cite a useful list of references for further in-depth study. In this age of international travel, their focus on acclimatization is appropriate. Those of us responsible for athletes who are likely to be performing in hot weather, especially with high humidity, need to be sure that the athletes have an adequate amount of time to acclimatize to the performance environment before participation. This may take as long as two weeks.
Great controversy exists, particularly among athletes and trainers, with regard to the appropriate form of fluid, carbohydrate, and electrolyte supplementation. Simple and clear guidelines are presented in this article that should serve to minimize controversy in this area.
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