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Article Title

THE IMPACT OF TEMPERATURE ON CRITICAL POWER DETERMINED BY A THREE MINUTE ALL-OUT TEST

Abstract

B.W. Kaiser1, K.K. Kruse2, B.M. Gibson1, K.J. Santisteban1, E.A. Larson1, B.W. Wilkins1, A.M. Jones, FACSM3, J.R. Halliwill, FACSM1, C.T. Minson, FACSM1

1University of Oregon, Eugene, OR; 2Harvard University, Cambridge, MA; 3University of Exeter, Exeter, UK

Critical Power (CP) separates the heavy and severe exercise domains, and work above CP (defined as W’) results in an inexorable progression to maximal oxygen uptake and a rise in blood lactate concentration to fatigue. The thermoregulatory demands accompanying a rise in body core temperature (Tc) compounded with the cardiovascular challenges presented by maximal exercise in a hot environment may impact CP and W’. To date, no study has explored the effects of Tc and environmental temperature on CP and W’. PURPOSE: The purpose of this study is to determine the effect of high environmental and Tc on CP. METHODS: CP was estimated as end test power (average of the last 30 sec) from a series of three-min “all out” tests (3MT). Volunteers (n=5, 3F) performed a 3MT on a familiarization visit and two experimental study days (thermoneutral and hot) in a randomized crossover design. Prior to the 3MT in both experimental conditions, subjects were immersed in either thermoneutral (36°C for 30min) or hot (40.5°C) water until Tc was ≥ 38.5°C. All 3MT were performed in an environmental chamber controlling for both temperature and humidity (18°C and 45% RH; 38°C and 40% RH for hot). RESULTS: Although variable, CP (mean ± SE) was modestly reduced from thermoneutral (226 ± 25W) to hot (223 ± 30W). Total work (mean ± SE) performed was moderately reduced between thermoneutral (51 ± 6 kJ) and hot (47 ± 5) conditions. Peak Power (mean ± SE) was comparable between thermoneutral (737 ± 174W) and hot (736 ± 125). W’ (mean ± SE) was reduced from thermoneutral (10 ± 1 kJ) to hot (7 ± 1). CONCLUSION: These preliminary data suggest that high Tc and environmental temperature appear to have a modest impact on CP as estimated by a 3-minute all-out test.

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