Impact of ambient temperature on energy cost and economical speed during level walking in healthy young males

Abstract

We measured oxygen consumption and carbon dioxide output during walking per unit distance (Cw) values for 14 healthy young males at seven speeds from 0.67 to 1.67 m s−1 (four min per stage) under thermoneutral (23°C), cool (13°C), and hot (33°C) environments. The Cw at faster gait speeds in the 33°C trial was slightly higher compared to those in the 23°C and 13°C trials. We found a significant main effect of speed and an interaction in the Cw though no significance in main effect of condition (P<0.05). Economical speed (ES) which can minimize the Cw in each individual was calculated from a U-shaped relationship. We found a significantly slower ES at 33°C [1.265 (0.060) m s−1 mean (s.d.)] compared to 23°C [1.349 (0.077) m s−1] and 13°C [1.356 (0.078) m s−1, P<0.05, respectively] with no differences between 23°C and 13°C (P>0.05). Heart rate and mean skin temperature responses in the 33°C condition increased throughout the walking trial compared to 23°C and 13°C (all P<0.05). These results suggest that an acute hot environment slowed the ES by∼7%, but an acute cool environment did not affect the Cw and ES.