Thermal responses and body fluid balance of competitive male swimmers during a training session.
Thermoregulatory and body fluid balance (BFB) responses of competitive swimmers were studied during a typical interval training session under natural field conditions. Subjects were 9 males (18.0 +/- 1.7 years; VO(2)max = 3.8 +/- 0.9 L x min(-1)) who covered 9,000 m in 180 minutes in an outdoor pool (mean water temperature = 26.8 +/- 0.3 degrees C; mean wet bulb globe temperature = 29.8 +/- 2.8 degrees C). Mean body weight (BWt) decreased by 1.8 +/- 0.5 kg (P < 0.05), and rectal temperature increased by 1.0 +/- 1.0 degrees C (P < 0.05). Volitional water intake (WI) (0.1 +/- 0.2 kg) did not maintain BFB (-0.5 kg per hour) and plasma volume decreased 10.7 +/- 5.4%. During a typical training session, swimmers experienced significant body fluid losses, and WI was not enough to prevent involuntary dehydration. The magnitude of the fluid losses (2.5% of BWt) was sufficient to compromise convective thermoregulation because of the decreased plasma volume. Hence, to prevent involuntary dehydration, swimmers should be encouraged to consume an amount of fluids that equals losses throughout the training sessions.
Soler
Reynaldo
R
Department of Recreation and Sports, San Juan, Puerto Rico.
Echegaray
Marcos
M
Rivera
Miguel A
MA
D000064:Acclimatization; D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D001833:Body Temperature Regulation / Q000502:physiology*; D006706:Homeostasis / Q000502:physiology*; D006801:Humans; D008297:Male; D010806:Physical Education and Training / Q000379:methods*; D010807:Physical Endurance; D011336:Probability; D012494:Sampling Studies; D013550:Swimming / Q000502:physiology*; D013997:Time Factors; D014882:Water-Electrolyte Balance / Q000502:physiology*