Fluid Replacement Strategies and Heart Rate Variability Recovery Following Prolonged Exercise in the Heat and Mild Dehydration
Ciara N. Manning,
Margaret C. Morrissey,
Sean P. Langan,
Rebecca L. Stearns,
Robert A. Huggins,
Ryan M. Curtis,
Yasuki Sekiguchi,
Srinivas Laxminarayan,
Jaques Reifman,
Douglas J. Casa
Affiliations
Ciara N. Manning
Korey Stringer Institute, Department of Kinesiology, University of Connecticut, Storrs, CT 06269-1110, USA
Margaret C. Morrissey
Korey Stringer Institute, Department of Kinesiology, University of Connecticut, Storrs, CT 06269-1110, USA
Sean P. Langan
Korey Stringer Institute, Department of Kinesiology, University of Connecticut, Storrs, CT 06269-1110, USA
Rebecca L. Stearns
Korey Stringer Institute, Department of Kinesiology, University of Connecticut, Storrs, CT 06269-1110, USA
Robert A. Huggins
Korey Stringer Institute, Department of Kinesiology, University of Connecticut, Storrs, CT 06269-1110, USA
Ryan M. Curtis
Korey Stringer Institute, Department of Kinesiology, University of Connecticut, Storrs, CT 06269-1110, USA
Yasuki Sekiguchi
Korey Stringer Institute, Department of Kinesiology, University of Connecticut, Storrs, CT 06269-1110, USA
Srinivas Laxminarayan
Department of Defense, Biotechnology High Performance Computing Software Applications Institute, Telemedicine and Advanced Technology Research Center, United States Army Medical Research and Development Command, Fort Detrick, MD 21702-5000, USA
Jaques Reifman
Department of Defense, Biotechnology High Performance Computing Software Applications Institute, Telemedicine and Advanced Technology Research Center, United States Army Medical Research and Development Command, Fort Detrick, MD 21702-5000, USA
Douglas J. Casa
Korey Stringer Institute, Department of Kinesiology, University of Connecticut, Storrs, CT 06269-1110, USA
Background: In sporting and combat settings, optimal fluid replacement is rarely achieved, exacerbating physiological strain. It is unknown if prescribed fluid replacement following exercise in heat impacts heart rate variability (HRV). Purpose: Compare prescribed drinking (PD) and ad libitum (AL) fluid replacement on HRV following exercise in heat. Methods: Twelve participants (26 ± 5 years, VO2max: 58.44 ± 7.05 mL·kg−1·min−1) completed three trials in heat (36 °C, 36% humidity) on separate days, and were placed into groups, PD or AL. Recovery was assessed ~24 h later (hydration and HRV). HRV time and frequency was measured using a 3-lead electrocardiogram. Two-way repeated measures analysis of variance measured changes in HRV pre-trial, post-trial, and follow-up between groups. Data reported: p-value, mean difference (MD). Results: Fluid consumption was greater in PD during recovery (p = 0.012, MD = 1245 mL). Both groups were euhydrated at follow-up. HRV time (p p 2) decreased post-trial and increased by follow-up (time, p p 2). HRV was similar between groups (p > 0.05). Conclusions: Replacing ≥60% fluid sufficiently rehydrates and restores HRV 24 h post-exercise in heat and mild dehydration (BML ≤ 3%). Prescribed fluid consumption during recovery was ~30% greater. Additional measures of recovery sensitive to heat strain may provide a more holistic understanding of specific mechanisms of recovery.
