Dehydration impairs cycling performance, independently of thirst: A blinded study

J. D. Adams, Yasuki Sekiguchi, Hyun Gyu Suh, Adam D. Seal, Cameron A. Sprong, Tracie W. Kirkland, Stavros A. Kavouras

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19 Scopus citations

Abstract

Purpose The aim of the present study was to examine the effect of dehydration on exercise performance independently of thirst with subjects blinded of their hydration status. Methods Seven male cyclists (weight, 72 ± 9 kg; body fat, 14% ± 6%; peak oxygen uptake, 59.4 ± 6 mL·kg -1 ·min -1 ) exercised for 2 h on a cycle ergometer at 55% peak oxygen uptake , in a hot-dry environment (35°C, 30% relative humidity), with a nasogastric tube under euhydrated-non-thirst (EUH-NT) and dehydrated-non-thirst (DEH-NT) conditions. In both trials, thirst was matched by drinking 25 mL of water every 5 min (300 mL·h -1 ). In the EUH-NT trial, sweat losses were fully replaced by water via the nasogastric tube (calculated from the familiarization trial). After the 2 h of steady state, the subjects completed a 5-km cycling time trial at 4% grade. Results Body mass loss for the EUH-NT and DEH-NT after the 2 h was -0.2% ± 0.6% and -2.2% ± 0.4%, whereas after the 5-km time trial, it was -0.7% ± 0.5% and 2.9% ± 0.4%, respectively. Thirst (35 ± 30 vs 42 ± 31 mm) and stomach fullness (46 ± 21 vs 35 ± 20 mm) did not differ at the end of the 2 h of steady state between EUH-NT and DEH-NT trials (P > 0.05). Subjects cycled faster during the 5-km time trial in the EUH-NT trial compared with the DEH-NT trial (23.2 ± 1.5 vs 22.3 ± 1.8 km·h -1 , P < 0.05), by producing higher-power output (295 ± 29 vs 276 ± 29 W, P < 0.05). During the 5-km time trial, core temperature was higher in the DEH-NT trial (39.2°C ± 0.7°C) compared with the EUH-NT trial (38.8°C ± 0.2°C; P > 0.05). Conclusions These data indicated that hypohydration decreased cycling performance and impaired thermoregulation independently of thirst, while the subjects were unaware of their hydration status.

Original languageEnglish (US)
Pages (from-to)1697-1703
Number of pages7
JournalMedicine and science in sports and exercise
Volume50
Issue number8
DOIs
StatePublished - Aug 1 2018
Externally publishedYes

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Keywords

  • CORE TEMPERATURE
  • DRINK
  • FLUID BALANCE
  • HYDRATION
  • HYPOHYDRATION
  • TIME TRIAL

ASJC Scopus subject areas

  • Orthopedics and Sports Medicine
  • Physical Therapy, Sports Therapy and Rehabilitation

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