Date of Completion

6-21-2016

Embargo Period

6-27-2016

Keywords

Hydration, Sleep, Neuromuscular Control, Fluid Balance

Major Advisor

Douglas J. Casa

Associate Advisor

Lawrence E. Armstrong

Associate Advisor

Lindsay J. DiStefano

Associate Advisor

Elaine C. Lee

Field of Study

Kinesiology

Degree

Doctor of Philosophy

Open Access

Open Access

Abstract

Maintaining an appropriate level of hydration has been shown to optimize performance and enhance safety during exercise in the heat. However, limited research exists examining the influence of exercise-induced dehydration on quality of sleep and measures of aerobic capacity and neuromuscular control. The purpose of this investigation sought to examine quality of sleep, aerobic capacity and neuromuscular control following prolonged exercise in the heat. Eleven participants (mean±SD; age, 22±3y; height, 178±6cm; VO2max, 54.3±5.4ml•kg-1•min-1; body fat, 11.6±3.9%) completed three exercise sessions in a climate-controlled chamber (ambient temperature, 35.3±0.6°C, relative humidity, 31.3±2.0%). Exercise consisted of 3 hours of exercise on a motorized treadmill followed by 60 minutes of passive rest in a climate-controlled chamber. Neuromuscular control and hematologic hydration measures were assessed before and after each exercise session. Objective and subjective sleep measures along with 24-hour urine were collected the night before and after the exercise session. Participants also arrived to the laboratory 24-30 hours the following day for assessment of hydration status via urinary and hematologic measures and measurements of aerobic capacity and neuromuscular control. Trials consisted of: 1) Participants arrived euhydrated and minimized their fluid losses during exercise and recovery (EUR), 2) Participants arrived euhydrated and progressively dehydrated during exercise and recovery (EUD), and 3) Participants arrived hypohydrated and progressively dehydrated during exercise and recovery (HYD). At the end of exercise, the level of hypohydration was 0.4±1.0%, 3.8±1.2% and 5.6±0.6% for EUR, EUD and HYD respectively. There were no differences in hydration status as measured by changes in body mass, urinary and hematologic markers between trials or rehydration groups the day following the exercise session of each trial. There were no differences between trial or rehydration group on objective or subjective measures of sleep; however, urine volume was predictive of improved subjective ratings of sleep. Additionally, there were no differences in measures of aerobic capacity or neuromuscular control between trials or rehydration groups the day following each exercise session. Moderate intensity exercise in the heat eliciting graded levels of hypohydration does not seem to adversely affect quality of sleep or neuromuscular control when assessed 24 hours following exercise.

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