Acute Cold Exposure Does Not Affect Gross Efficiency During Cycling

Abstract

PURPOSE: Gross efficiency (GE) is known to decrease during exercise in the heat, but the effect of low ambient temperatures on GE is poorly understood. This study aims to investigate the effect of acute cold exposure on GE during steady state cycling before and after a time-trial. METHODS: Twenty-one, task habituated, male cyclists (age 26 ± 4 year, VO2max 60.1 ± 6.7 mL/kg/min) completed three cycling tests in temperatures of -15 °C, 0 °C and 20 °C. The exercise test consisted of a submaximal exercise bout between 55 and 65% VO2max before and after a 2500-m self-paced time trial. GE was calculated over a 3-min interval at the end of each submaximal block. The effect of acute cold exposure on body temperature was evaluated by measuring core body temperature and skin temperature on different locations. RESULTS: A multilevel linear model revealed that ambient temperature did not affect GE (&#935;2 (7) = 2.531, p = 0.282). Performing a time-trial had a significant effect on GE (&#935;2 (8) = 13.3967, p < 0.001), resulting in a lower GE after the time trial compared to before (pre: 20.6 ± 1.1%, post: 19.9 ± 1.1%, t = -5.542, p < 0.001). The decline in GE after performing a time-trial was not altered by ambient temperature (&#935;2 (7) = 3.57, p = 0.168). Acute cold exposure did not affect core body temperature (&#935;2 (7) = 0.470, p = 0.791), but mean skin temperature was significantly lower in -15 °C and 0 °C compared to 20 °C (-15 °C: 25.88 ± 1.06 °C, 0 °C: 27.32 ± 1.16 °C, 20 °C: 31.18 ± 0.78 °C, p < 0.003). CONCLUSION: Acute cold exposure did not affect GE during submaximal steady state cycling exercise performed before and after a time-trail. Low ambient temperatures resulted in lower skin temperatures, but core body temperature remained unaffected.