Rates of fluid ingestion alter pacing but not thermoregulatory responses during prolonged exercise in hot and humid conditions with appropriate convective cooling

  • J. P. Dugas
  • U. Oosthuizen
  • R. Tucker
  • T. D. Noakes
Original Article

Abstract

The aim of the study was to examine the effects of fluid replacement on thermoregulation and cycling performance in hot, humid conditions. Six male cyclists (PPO = 426 ± 39 W) performed six 80 km time trials. Subjects replaced 0% (0); 33% (33); 66% (66); or 100% (100) of the weight lost during an “ad libitum” trial (Ad Lib). In another condition (WET), subjects rinsed their mouths at 10 km intervals. There was no trial effect on any thermoregulatory variables or on performance. When WET, 0, 33 (“LO”) were compared to Ad Lib; 66, 100 (“HI”), power output was higher in HI (209 ± 22 vs. 193 ± 22 W, p < 0.05). Restricting fluid below ad libitum rates impaired performance (LO group). Rates greater than ad libitum did not result in further improvements. Ad libitum fluid ingestion is optimal as it prevents athletes from ingesting too little or too much fluid.

Keywords

Heat Rectal temperature Temperature Cycling Performance Exercise Time trial Dehydration Anticipatory regulation Fluid balance 

Copyright information

© Springer-Verlag 2008

Authors and Affiliations

  • J. P. Dugas
    • 1
    • 2
  • U. Oosthuizen
    • 1
  • R. Tucker
    • 1
  • T. D. Noakes
    • 1
  1. 1.UCT/MRC Research Unit for Exercise Science and Sports Medicine, Department of Human BiologyUniversity of Cape Town, Sports Science InstituteCape TownSouth Africa
  2. 2.ChicagoUSA

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