EFFECT OF FLUID TEMPERATURE AND VOLUME ON THERMOREGULATION IN THE HEAT

Author

Michelle M. Johannsen, University of Montana, MissoulaFollow

Year of Award

2016

Document Type

Thesis

Degree Type

Master of Science (MS)

Degree Name

Health and Human Performance (Exercise Science Option)

Department or School/College

Department of Health and Human Performance

Committee Chair

Brent Ruby

Commitee Members

Charles Dumke, Stephen Lodmell

Keywords

thermoregulation, hydration, performance, heat stress, physiological strain index, core temperature

Subject Categories

Sports Sciences | Translational Medical Research

Abstract

The link between thermoregulation, hydration status, and exercise performance in hot humid environments is controversial. The purpose of this study was to evaluate the effects of volume and temperature of ingested fluid on hydration status, thermoregulation and exercise performance. Recreationally active males (N=11, 24.7±5.9 years; VO₂max=58.2±6.0 mL/kg/min) completed two 3-hour intermittent exercise trials in the heat (31^o WBGT=35.5°C with 50% humidity). Participants consumed either 1 mL/kg body weight (BW) of room temperature water (35.5°C; ROOM) or 0.5 mL/kg of an ice slurry mixture (~0°C; COLD) every ten minutes throughout the trials in a randomized crossover design. Subjects walked on a motorized treadmill at 40% VO₂max for 25-minutes followed by 5-minutes of standing rest after which a 1.6 km time trial was completed as quickly as possible on a non-motorized treadmill (Woodway Curve). After completion of the time trial, participants remained seated for the rest of the 1-hour time period. This series of steady state (SS) and time trial (TT) segments was repeated three times over each 3-hour trial. Core temperature and heart rate were monitored continuously throughout the 3-hour trials and used to calculate physiological strain index (PSI). Nude BW was measured pre and post to calculate sweat loss. Body weight loss was significantly higher for the COLD trial (2.2±0.7 and 3.0±0.8 % for the ROOM and COLD respectively, p<0.05). Total water loss was not different between the trials (1.2±0.2 and 1.2±0.2 L/hr, for the ROOM and COLD, respectively). Time trial performance was not different between treatments (ROOM: 9.7±1.3, 10.8±1.4, 12.8±2.4 min for hours 1, 2, and 3, respectively, and COLD: 10.1±1.6, 11.2±2.0, 12.8±2.6 min for hours 1, 2, and 3, respectively) but was impaired over time. These data suggest that it is not simply the volume, but the temperature of the ingested fluid that aids in thermoregulation.

Recommended Citation

Johannsen, Michelle M., "EFFECT OF FLUID TEMPERATURE AND VOLUME ON THERMOREGULATION IN THE HEAT" (2016). Graduate Student Theses, Dissertations, & Professional Papers. 10706.
https://scholarworks.umt.edu/etd/10706