Health, Exercise, and Sports Sciences ETDs

Roy Salgado

Publication Date

9-12-2014

Abstract

Heat acclimation is known to increase exercise economy. Previous examinations suggest heat acclimation may preserve performance at altitude. This study examined the effect of using heat acclimation as a cross environmental stressor to improve exercise economy and efficiency during acute exercise at altitude. Eight trained males (VO2peak: 53.3 ± 6.7 ml/kg/min) performed maximal exercise tests, submaximal exercise bouts, and heat tolerance testing in a temperate environment (21°C) at 1600 m and 4350 m before and after a 10-day heat acclimation (40\uf0b0C and 20% RH) on a cycle ergometer (~43% peak power). To investigate heat stress mechanisms, C2C12 myocytes were heat stressed for 24 hours (40°C, 5% CO2). Heat acclimation did not alter VO2peak at 1600 m (53.3 ± 6.7 vs. 53.7 ± 3.7 ml/kg/min, p > 0.05) or 4350 m (45.3 ± 4.1 versus 45.9 ± 3.4 ml/kg/min, p > 0.05). Heat acclimation increased exercise economy by 1.6% and 2% in the low intensity and high intensity exercise, respectively at 1600 m with only a 0.48% increase at 4350 m. In the cell study, heat stress significantly reduced UCP3 expression, reduced mitochondrial uncoupling (71.1% ±1.2%) and suppressed basal and peak oxidative metabolism (75.5% ± 4.9% and 64.4% ± 5.9%, respectively) compared to control. Heat stress also significantly increased PGC-1α, NRF1 and TFAM leading to increased mitochondrial content. These data demonstrate that while heat stress reduces UCP3 expression, thereby reducing uncoupling and leading to enhanced mitochondrial efficiency, these adaptations are not observed in the whole body. At this time, I am unable definitively promote the use of heat acclimation as a cross environmental stressor for acute exercise at altitude.

Keywords

Altitude, hypoxia, Heat Tolerance, Exercise Capacity, Skeletal Muscle

Document Type

Dissertation

Language

English

Degree Name

Exercise Science

Level of Degree

Doctoral

Department Name

Health, Exercise, and Sports Sciences

First Committee Member (Chair)

Parker, Daryl

Second Committee Member

Suzanne, Schneider

Third Committee Member

Kravitz, Len

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