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Blinded and unblinded hypohydration similarly impair cycling time trial performance in the heat in trained cyclists

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journal contribution
posted on 28.03.2019, 09:16 by Mark P. Funnell, Stephen MearsStephen Mears, Kurt Bergin-Taylor, Lewis JamesLewis James
Knowledge of hydration status may contribute to hypohydration-induced exercise performance decrements, therefore, this study compared blinded and unblinded hypohydration on cycling performance. Fourteen trained, non-heat acclimated cyclists (age 25 ± 5 y; V̇O2peak 63.3 ± 4.7 mL∙kg-1∙min-1; cycling experience 6 ± 3 y) were pair-matched to blinded (B) or unblinded (UB) groups. After familiarisation, subjects completed euhydrated (B-EUH; UB-EUH) and hypohydrated (B-HYP; UB-HYP) trials in the heat (31˚C); 120 min cycling preload (50% Wpeak) and a time trial (~15 min). During the preload of all trials, 0.2 mL water∙kg body mass-1 was ingested every 10 min, with additional water provided during EUH trials to match sweat losses. To blind the B group, a nasogastric tube was inserted in both trials and used to provide water in B-EUH. The preload induced similar ( P=0.895) changes in body mass between groups (B-EUH -0.6 ± 0.5%; B-HYP -3.0 ± 0.5%; UB-EUH -0.5 ± 0.3%; UB-HYP -3.0 ± 0.3%). All variables responded similarly between B and UB groups ( P≥0.558), except thirst ( P=0.004). Changes typical of hypohydration (increased heart rate, RPE, gastrointestinal temperature, serum osmolality and thirst, decreased plasma volume; P≤0.017) were apparent in HYP by 120 min. Time trial performance was similar between groups ( P=0.710) and slower ( P≤0.013) with HYP for B (B-EUH 903 ± 89 s; B-HYP 1008 ± 121 s; -11.4%) and UB (UB-EUH 874 ± 108 s; UB-HYP 967 ± 170 s; -10.1%). Hypohydration of ~3% body mass impairs time trial performance in the heat, regardless of knowledge of hydration status.

Funding

This research was supported by the NIHR Leicester Biomedical Research Centre.

History

School

  • Sport, Exercise and Health Sciences

Published in

Journal of Applied Physiology

Volume

126

Issue

4

Pages

870-879

Citation

FUNNELL, M.P. ... et al, 2019. Blinded and unblinded hypohydration similarly impair cycling time trial performance in the heat in trained cyclists. Journal of Applied Physiology, 126(4), pp. 870-879.

Publisher

© the American Physiological Society

Version

AM (Accepted Manuscript)

Publisher statement

This paper was accepted for publication in the journal Journal of Applied Physiology and the definitive published version is available at https://doi.org/10.1152/japplphysiol.01026.2018.

Acceptance date

06/01/2019

Publication date

2019-04-02

Copyright date

2019

ISSN

8750-7587

eISSN

1522-1601

Language

en