Economical and preferred walking speed using body weight support apparatus with a spring-like characteristics.

Background: 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). 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.

Methods: We measured oxygen uptake and carbon dioxide output to calculate CoT values at seven treadmill walking speeds (0.67-2.00 m s) in 40 healthy young males under normal walking (NW) and BWS. The PWS was determined under both conditions on a different day.

Results: A spring-like behavior of our BWS apparatus reduced the CoT values at 1.56, 1.78, and 2.00 m s. The ES with BWS (1.61 ± 0.11 m s) was faster than NW condition (1.39 ± 0.06 m s). A Bland-Altman analysis indicated that there were no systematic biases between ES and PWS in both conditions.

Conclusions: The 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.