Self-selected fluid volume and flavor strength does not alter fluid intake, body mass loss, or physiological strain during moderate-intensity exercise in the heat

Nathan J Deming; Kyle W Carr; Jacob L Anna; Brianna R Dupre; Meghan E Smith; Frank A Dinenno; Jennifer C Richards

doi:10.1016/j.jtherbio.2020.102575

Self-selected fluid volume and flavor strength does not alter fluid intake, body mass loss, or physiological strain during moderate-intensity exercise in the heat

J Therm Biol. 2020 Apr:89:102575. doi: 10.1016/j.jtherbio.2020.102575. Epub 2020 Mar 23.

Authors

Nathan J Deming¹, Kyle W Carr², Jacob L Anna³, Brianna R Dupre³, Meghan E Smith³, Frank A Dinenno³, Jennifer C Richards⁴

Affiliations

¹ Human Cardiovascular Physiology Laboratory, Department of Health and Exercise Science, Colorado State University, Fort Collins, CO, 80521, USA; Air Force Institute of Technology, Wright-Patterson Air Force Base, OH, 45433, USA.
² Human Cardiovascular Physiology Laboratory, Department of Health and Exercise Science, Colorado State University, Fort Collins, CO, 80521, USA; Honors College, Colorado State University, Fort Collins, CO, 80521, USA.
³ Human Cardiovascular Physiology Laboratory, Department of Health and Exercise Science, Colorado State University, Fort Collins, CO, 80521, USA.
⁴ Human Cardiovascular Physiology Laboratory, Department of Health and Exercise Science, Colorado State University, Fort Collins, CO, 80521, USA. Electronic address: jennifer.richards@colostate.edu.

PMID: 32364968
DOI: 10.1016/j.jtherbio.2020.102575

Abstract

Introduction: The purpose of this study was to determine the effects of ad libitum flavor and fluid intake on changes in body mass (BM) and physiological strain during moderate intensity exercise in the heat.

Methods: Ten subjects (24±3yrs, 7M/3F) performed 60 min of treadmill walking at 1.3 m/s and 7% grade in an environmental chamber set to 33 °C and 10% relative humidity while carrying a 22.7 kg pack on two different occasions. Subjects consumed either plain water or water plus flavor (Infuze), ad libitum, at each visit. Pre and post exercise, fluid consumption (change in fluid reservoir weight) and BM (nude) were measured. During exercise, heart rate (HR), systolic blood pressure (SBP), rate of perceived exertion (RPE), oxygen consumption (VO₂), respiratory exchange ratio (RER), core temperature (T_C), and physiological strain index (PSI) were recorded every 15 min during exercise.

Results: No significant differences were observed for fluid consumption between fluid conditions (512 ± 97.2 mL water vs. 414.3 ± 62.5 mL Infuze). Despite a significant decrease from baseline, there were no significant differences in overall change of BM (Δ -1.18 vs. -0.64 Kg) or percent body weight loss for water and Infuze conditions, respectively (1.58 ± 0.6 and 0.79 ± 0.2%). Furthermore, there were no significant differences in HR (144 ± 6 vs. 143 ± 8 bpm), SBP (157 ± 5 vs. 155 ± 5 mmHg), RPE, VO₂ (27.4 ± 0.9 vs. 28.1 ± 1.2 ml/Kg/min), RER, T_C (38.1 ± 0.1 vs. 37.0 ± 0.1 °C), and peak PSI (5.4 ± 0.4 vs. 5.7 ± 0.8) between conditions.

Conclusions: Offering individuals the choice to actively manipulate flavor strength did not significantly influence ad libitum fluid consumption, fluid loss, or physiological strain during 60 min of moderate intensity exercise in the heat.

MeSH terms

Adolescent
Adult
Body Temperature Regulation
Drinking / drug effects*
Flavoring Agents / pharmacology*
Hot Temperature*
Humans
Male
Physical Conditioning, Human / methods*
Physical Exertion / drug effects*
Random Allocation
Water Loss, Insensible / drug effects*
Weight Loss / drug effects

Substances

Flavoring Agents