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Open AccessArticle

Hiking Time Trial Performance in the Heat with Real-Time Observation of Heat Strain, Hydration Status and Fluid Intake Behavior

1
College of Health Solutions, Arizona State University, Phoenix, AZ 85004, USA
2
School of Geographical Sciences and Urban Planning, Arizona State University, Tempe, AZ 85281, USA
*
Author to whom correspondence should be addressed.
Int. J. Environ. Res. Public Health 2020, 17(11), 4086; https://doi.org/10.3390/ijerph17114086
Received: 30 April 2020 / Revised: 29 May 2020 / Accepted: 4 June 2020 / Published: 8 June 2020
This study investigated the real-time progression of heat strain in mountain hikers during time trials (TT). Participants (n = 12; 7M/5F; age 21.6 ± 2.47) attempted to climb Tempe Butte (~1.1 mi) four times in HOT and MOD trials (wet bulb globe temperature 31.6 °C vs. 19.0 °C). Performance, physiological outcomes, and fluid intake behavior were measured in real-time. Hot conditions significantly impaired hiking TT performance by 11%, reduced aerobic capacity by 7%, increased peak rate of perceived exertion (RPE) by 19%, and elevated core temperature (Tc) by 0.7 °C compared to MOD (all p < 0.03). Less-aerobically-fit participants were most negatively-affected by heat stress. Based on sweat lost, participants in HOT required 2.26 ± 0.91 L of fluids, brought 1.52 ± 0.83 L, and consumed 1.54 ± 0.49 L, losing an average of 1.1% ± 1.0%BM. Participants in MOD required 1.28 ± 0.39 L of fluids, brought 1.57 ± 1.09 L, and consumed 0.79 ± 0.57 L, losing an average of 1.0% ± 0.8%BM. Morning-after urine specific gravity (USG) values revealed 75% of hikers were hypohydrated (USG ≥ 1.020) after HOT; 67% after MOD. Heat stress impairs hiking TT performance while increasing RPE and Tc. Fitter participants showed less performance and physiological impairment from heat stress. Although hikers in both conditions lost similar body weight, hikers were limited in HOT by fluid availability, whereas in MOD, fluid was available and dehydration was voluntary. View Full-Text
Keywords: exertional heat illness (EHI); heat strain; heat stress; mountain search and rescue; biometeorology; dehydration; dietary behavior; public health and safety exertional heat illness (EHI); heat strain; heat stress; mountain search and rescue; biometeorology; dehydration; dietary behavior; public health and safety
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MDPI and ACS Style

Linsell, J.D.; Pelham, E.C.; Hondula, D.M.; Wardenaar, F.C. Hiking Time Trial Performance in the Heat with Real-Time Observation of Heat Strain, Hydration Status and Fluid Intake Behavior. Int. J. Environ. Res. Public Health 2020, 17, 4086. https://doi.org/10.3390/ijerph17114086

AMA Style

Linsell JD, Pelham EC, Hondula DM, Wardenaar FC. Hiking Time Trial Performance in the Heat with Real-Time Observation of Heat Strain, Hydration Status and Fluid Intake Behavior. International Journal of Environmental Research and Public Health. 2020; 17(11):4086. https://doi.org/10.3390/ijerph17114086

Chicago/Turabian Style

Linsell, Joshua D.; Pelham, Emily C.; Hondula, David M.; Wardenaar, Floris C. 2020. "Hiking Time Trial Performance in the Heat with Real-Time Observation of Heat Strain, Hydration Status and Fluid Intake Behavior" Int. J. Environ. Res. Public Health 17, no. 11: 4086. https://doi.org/10.3390/ijerph17114086

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