Deakin University
Browse

File(s) under permanent embargo

Ad libitum drinking adequately supports hydration during 2 h of running in different ambient temperatures

Version 2 2024-06-04, 14:30
Version 1 2018-10-26, 15:24
journal contribution
posted on 2024-06-04, 14:30 authored by MD Hoffman, Rhiannon SnipeRhiannon Snipe, RJS Costa
Purpose: To examine if ad libitum drinking will adequately support hydration during exertional heat stress. Methods: Ten endurance-trained runners ran for 2 h at 60% of maximum oxygen uptake under different conditions. Participants drank water ad libitum during separate trials at mean ambient temperatures of 22 °C, 30 °C and 35 °C. Participants also completed three trials at a mean ambient temperature of 35 °C while drinking water ad libitum in all trials, and with consumption of programmed glucose or whey protein hydrolysate solutions to maintain euhydration in two of these trials. Heart rate, oxygen uptake, rectal temperature, perceived effort, and thermal sensation were monitored, and nude body mass, hemoglobin, hematocrit, and plasma osmolality were measured before and after exercise. Water and mass balance equations were used to calculate hydration-related variables. Results: Participants adjusted their ad libitum water intake so that the same decrease in body mass (1.1–1.2 kg) and same decrease in body water (0.8–0.9 kg) were observed across the range of ambient temperatures which yielded significant differences (p <.001) in sweat loss. Overall, water intake and total water gain replaced 57% and 66% of the water loss, respectively. The loss in body mass and body water associated with ad libitum drinking resulted in no alteration in physiological and psychophysiological variables compared with the condition when hydration was nearly fully maintained (0.3 L body water deficit) relative to pre-exercise status from programmed drinking. Conclusions: Ad libitum drinking is an appropriate strategy for supporting hydration during running for 2 h duration under hot conditions.

History

Journal

European journal of applied physiology

Volume

118

Pagination

2687-2697

Location

Berlin, Germany

ISSN

1439-6319

Language

eng

Publication classification

C1 Refereed article in a scholarly journal

Copyright notice

2018, This is a U.S. government work and its text is not subject to copyright protection in the United States; however, its text may be subject to foreign copyright protection.

Issue

12

Publisher

Springer

Usage metrics

    Research Publications

    Exports

    RefWorks
    BibTeX
    Ref. manager
    Endnote
    DataCite
    NLM
    DC