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Date of Award

2019

Document Type

Campus Access Dissertation

Degree Name

Doctor of Philosophy in Integrative Physiology (PhD)

Administrative Home Department

Department of Kinesiology and Integrative Physiology

Advisor 1

Steven Elmer

Committee Member 1

Tejin Yoon

Committee Member 2

Kevin Trewartha

Committee Member 3

Min Wang

Committee Member 4

Phillip Watts

Abstract

This dissertation used a variety of methods including functional near-infrared spectroscopy, surface electromyography, electrical stimulation, load cells and psychological questionnaires to investigate how changes in temperature can alter neuromuscular fatigue, prefrontal cortex (PFC) activation, and the perception of discomfort during upper extremity exercise. In the first study, I examined how cold ambient temperatures affect climbing specific finger flexor performance. Exposure to 10°C for 30 min did not hinder maximal finger flexor strength, however time to failure during the fatiguing task was greater (364 ± 135 vs. 251 ± 97 s; P < 0.01) compared to performance in a thermoneutral environment (24°C). In the second study, I investigated how heating and cooling arm musculature prior to exercise influences PFC activation, neuromuscular function and perceptual demands during a fatiguing task of the elbow flexors. Performance of a low intensity contraction for 5 min resulted in greater PFC oxygenation in the hot (13.3 ± 4.5 μmol/L) and neutral conditions (12.4 ± 4.4 μmol/L) compared to the cold condition (10.3 ± 3.8 μmol/L; P < 0.001). Reductions in maximal strength were greater for the hot (25.7 ± 8.4%) and neutral (22.2 ± 9.6%) conditions compared to the cold condition (17.5 ± 8.9%; P < 0.01). Lastly, perceptual demands were lower in the cold condition. In the third study, I explored how passive recovery vs. cold water immersion of the forearms affected repeated climbing specific finger flexor performance, PFC activation, muscle fatigue and perceptual demands. Following the cold water immersion recovery intervention, time to task failure was greater (243 ± 78 vs. 154 ± 43 s; P < 0.001) compared to passive recovery. This improvement was accompanied by a slower increase in PFC activation (3.60 ± 1.64 vs. 5.38 ± 2.63 µmol/L/min; P < 0.01). Additionally, muscle discomfort and muscle fatigue were similar at the end of the fatiguing task, despite a longer time to failure following cold water immersion. Taken together, these results provide psychophysiological evidence that cooling can improve muscle performance, reduce PFC activation and alleviate perceptual demands during low to moderate intensity fatiguing contractions of the upper extremities.

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