The Impact of Temperature on Critical Power Determined by a Three Minute All‐Out Test

Abstract

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 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 elevated Tc and environmental temperature on CP and W′. The purpose of this study is to determine the effect of high environmental and Tc on CP and W′. 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=7, 3F) performed a 3MT during 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 30 min) 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 for thermoneutral; 38°C and 40% RH for hot). A paired t‐test was used for statistical analysis and data are presented as mean ± SE. Although variable, CP was similar between thermoneutral (245 ± 22W) and hot (243 ± 25; p=0.83), while W’ was only mildly reduced from thermoneutral (11 ± 1 kJ) to hot (9 ± 2) p=0.17. Total work performed was similar between thermoneutral (55 ± 5 kJ) and hot (53 ± 5) conditions (p=0.27) and peak power was similar between thermoneutral (827 ± 89W) and hot (809 ± 85) p=0.49. These preliminary data suggest that high Tc and environmental temperature, per se, appear to have no significant impact on CP as estimated by a 3‐minute all‐out test.