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Original Research ARTICLE Provisionally accepted The full-text will be published soon. Notify me

Front. Physiol. | doi: 10.3389/fphys.2019.00507

The efficacy of ingesting water on thermoregulatory responses and running performance in a warm-humid condition.

 Ahmad M. Che Muhamed1*, Hazwani Ahmad Yusof1, Stephen R. Stannard2,  Toby Mündel2 and Martin W. Thompson3
  • 1Lifestyle Science Cluster, Advanced Medical and Dental Institute, University of Science, Malaysia, Malaysia
  • 2School of Sport, Exercise and Nutrition, College of Health, Massey University, New Zealand
  • 3Faculty of Health Sciences, University of Sydney, Australia

The understanding that fluid ingestion attenuates thermoregulatory and circulatory stress during exercise in the heat was based on studies conducted in relatively dry (~ 50% RH) environments. It remains undetermined whether similar effects occur during exercise in a warm and more humid environment, where evaporative capacity is reduced. Nine well-trained, unacclimatised male runners were randomly assigned to perform 4 experimental trials where they ran for 60 min at an intensity of 70% VO2max followed by an incremental exercise test until volitional exhaustion. The 4 trials consisted of non-fluid ingestion (NF) and fluid ingestion (FI) in a warm-dry (WD) and warm-humid condition (WH). Time to exhaustion (TTE), body temperature (Tb), whole body sweat rate, partitional calorimetry measures, heart rate and plasma volume were recorded during exercise. There was no significant difference in Tb following 60 min of exercise in FI and NF trial within both WD (37.30C  0.4 vs. 37.40C  0.3; p > 0.05) and WH conditions (38.00C  0.4 vs. 38.10C  0.4; p > 0.05). The TTE was similar between FI and NF trials in both WH and WD, whereas exercise capacity was significantly shorter in WH than WD (9.1  2.8 min vs. 12.7  2.4 min, respectively; p = 0.01).
Fluid ingestion failed to provide any ergogenic benefit in attenuating thermoregulatory and circulatory stress during exercise in the WH and WD conditions. Consequently, exercise performance was not enhanced with fluid ingestion in the warm-humid condition, although the humid environment detrimentally affected exercise endurance.

Keywords: Fluid ingestion, thermoregulation, Circulation, relative humidity, Running performance

Received: 03 Nov 2018; Accepted: 11 Apr 2019.

Edited by:

Gary W. Mack, Brigham Young University, United States

Reviewed by:

Keiji Hayashi, University of Shizuoka, Japan
Zachary Schlader, University at Buffalo, United States
Kei Nagashima, Waseda University, Japan  

Copyright: © 2019 Che Muhamed, Ahmad Yusof, Stannard, Mündel and Thompson. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Prof. Ahmad M. Che Muhamed, Lifestyle Science Cluster, Advanced Medical and Dental Institute, University of Science, Malaysia, Penang, Malaysia, ahmadmunir@usm.my