Core temperature and sweat responses in professional women's tennis players during tournament play in the heat.

CONTEXT: Tennis is often played in hot, humid environments, intensifying the thermoregulatory strain placed on the athletes. As a safety measure, some tennis organizations allow for a 10-minute break in play between the second and third sets when environmental conditions are extreme. However, the actual effect of these breaks in reducing core temperature is unknown.
OBJECTIVE: To determine change in core temperature after a 10-minute break in play and assess fluid balance in professional female tennis players during tournament matches in the heat.
DESIGN: Cross-sectional study.
SETTING: A Women's Tennis Association Tour-sanctioned outdoor tournament on hard courts under hot conditions (30.3°C ± 2.3°C). PATIENTS OR OTHER PARTICIPANTS: Seven professional tennis players. MAIN OUTCOME MEASURE(S): Change in core temperature after a 10-minute break in tournament play, fluid intake, and sweat losses during match play.
RESULTS: Core temperature was reduced from 38.92°C to 38.67°C (change of -0.25°C ± 0.20°C) when a break was taken (P  =  .02). Mean sweat rate during match play was 2.0 ± 0.5 L/h. During that time, mean fluid intake was 1.5 ± 0.5 L/h, resulting in a 1.2% ± 1.0% reduction in body mass.
CONCLUSIONS: Female professional tennis players are subjected to high heat loads during match play in hot environments. However, a 10-minute break in play decreased core temperature in 6 of 7 players by an average of 0.25°C, indicating that the break provides practical benefits in the field. Furthermore, although mean sweat rate in this group of female tennis players was high, most athletes were still able to minimize mass loss to less than 2% of their prematch weight.