Predicting the Metabolic Cost of Level-Ground Walking from Gait Speed and Prosthesis Stiffness

Abstract

The number of individuals requiring the use of a prosthetic limb continues to rise each year. Use of a prosthesis may help improve health and mobility; however, quality of life (QOL) remains lower for many individuals with limb loss compared to their counterparts with intact limbs. One reason for the lower QOL is due to an increased metabolic demand while walking. Prior research has investigated the effects of prosthesis stiffness and gait speed on metabolic demands. However, few studies explore the effects of these variables while using a variable stiffness foot (VSF) prosthesis. Therefore, the purpose of this study was to use the novel VSF prosthesis to develop a regression model which predicts metabolic demand based on gait speed and prosthesis stiffness settings. This model could be used to help customize prosthesis performance for the user. Five participants were recruited and three were analyzed for this study. The effect of gait speed on metabolic demand was significant (p < 0.001) while the effect of stiffness settings was not statistically significant (p = 0.199). There were statistical differences in metabolic cost across the gait speeds in 4 of the 5 stiffness settings (α = 0.013). The regression model had an adjusted R2 value of 0.842 with a normalized root mean square error (NRMSE) of 7.02%. While these differences suggest prosthesis stiffness settings do not have a large effect on metabolic expenditure, subject-specific case studies show that prosthesis settings need to be considered when attempting to lower the metabolic demands of a lower-limb prosthesis.