Energetic Contribution of the Human Plantar Aponeurosis to Locomotor Economy During Bipedal Walking and Running.

OBJECTIVES: The human plantar aponeurosis (PA) is a unique structure that spans the longitudinal arch of the foot, contributing to locomotor efficiency by storing and releasing elastic energy. It is traditionally believed that the PA primarily enhances running economy by reducing muscular effort and metabolic cost. However, the extent to which the PA contributes to walking versus running has not been quantitatively assessed. This study aims to quantitatively compare the mechanical contribution of the PA during walking and running, and to evaluate its relative contribution to whole-body metabolic energy expenditure per unit distance in each gait. MATERIALS AND METHODS: This study investigated the role of the PA in human locomotion by comparing its mechanical contribution during walking and running in 10 healthy adults. Using a detailed foot model and motion capture technology, we quantified PA strain, force, power, and energy release during gait cycles. RESULTS: Peak power and shortening velocity were higher in running, resulting in a significantly larger total energy released by the PA per gait cycle. However, the relative contribution of PA energy to overall metabolic energy expenditure per distance was significantly greater during walking (1.8%) compared to running (1.1%), despite the greater absolute energy output during running. DISCUSSION: These findings challenge the prevailing view that the PA evolved primarily to enhance running efficiency. Instead, the results suggest that the PA plays a relatively larger role in reducing energy consumption during walking, shedding light on the evolutionary adaptation of the human foot for bipedal locomotion.