CoT-speed relationships under normal walking (NW) and BWS. The CoT values were lower with BWS (open circles; y = 1.987x2 − 6.325x + 8.191, r = 0.998, n = 40) than NW (black filled squares; y = 2.709x2 − 7.533x + 8.569, r = 0.990, n = 40) at faster than 1.56 m s− 1. A faster economical speed (ES) was observed with BWS than NW due to a rightward (faster) shift of the U-shaped CoT-speed relationship. Broken and solid arrows indicate the average ES with BWS and NW, respectively. $ p < 0.001 between BWS and NW at each walking speed. Values are mean ± standard deviation (SD).