Abstract
BackgroundA specific walking speed minimizing the U-shaped relationship between energy cost of transport per unit distance (CoT) and speed is called economical speed (ES). To investigate the effects of reduced body weight on the ES, we installed a body weight support (BWS) apparatus with a spring-like characteristics. We also examined whether the 'calculated' ES was equivalent to the 'preferred' walking speed (PWS) with 30% BWS.MethodsWe measured oxygen uptake and carbon dioxide output to calculate CoT values at seven treadmill walking speeds (0.67–2.00 m s− 1) in 40 healthy young males under normal walking (NW) and BWS. The PWS was determined under both conditions on a different day.ResultsA spring-like behavior of our BWS apparatus reduced the CoT values at 1.56, 1.78, and 2.00 m s− 1. The ES with BWS (1.61 ± 0.11 m s− 1) was faster than NW condition (1.39 ± 0.06 m s− 1). A Bland-Altman analysis indicated that there were no systematic biases between ES and PWS in both conditions.ConclusionsThe use of BWS apparatus with a spring-like behavior reduced the CoT values at faster walking speeds, resulting in the faster ES with 30% BWS compared to NW. Since the ES was equivalent to the PWS in both conditions, the PWS could be mainly determined by the metabolic minimization in healthy young males. This result also derives that the PWS can be a substitutable index of the individual ES in these populations.
Highlights
A specific walking speed minimizing the U-shaped relationship between energy cost of transport per unit distance (CoT) and speed is called economical speed (ES)
The CoT values were significantly decreased by 9.2% (1.56 m s− 1), 15.6% (1.78 m s− 1), and 20.8% (2.00 m s− 1) with body weight support (BWS) than normal walking (NW), but not at speeds slower than 1.33 m s− 1 (F = 7.901, p = 0.006; Fig. 2)
A significantly faster ES was observed with BWS (1.61 ± 0.11 m s− 1) than NW (1.39 ± 0.06 m s− 1) (t = 11.420, p < 0.001; Fig. 2)
Summary
A specific walking speed minimizing the U-shaped relationship between energy cost of transport per unit distance (CoT) and speed is called economical speed (ES). Abe et al BMC Sports Sci Med Rehabil (2021) 13:107 or moderate exercise intensities [13], assuming that the effect of BWS on the U-shaped CoT-speed relationship in walking could be greater at faster speeds than slower speeds. These assumptions suggested that a rightward (faster) shift of the U-shaped CoT-speed relationship would be observed with BWS compared to normal walking (NW). Since a rightward shift of the U-shaped CoT-speed relationship provides a faster ES [15], we hypothesized that the ES would be faster with BWS compared to NW conditions
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