The effect of foot compliance encoded in the windlass mechanism on the energetics of human walking

The human foot, which is the part of the body that interacts with the environment during locomotion, consists of rich biomechanical design. One of the unique designs of human feet is the windlass mechanism. In a previous simulation study, we found that the windlass mechanism seems to improve the energy efficiency of walking. To better understand the origin of this efficiency, we here conduct both simulation and experimental studies exploring the influence of foot compliance, which is one of the functionalities that the windlass mechanism embeds, on the energetics of walking. The studies show that walking with compliant feet incurs more energetic costs than walking with stiff feet. The preliminary results suggest that the energy saved by introducing the windlass mechanism does not originate from the compliance it embeds. We speculate that the energy savings of the windlass mechanism are related more to its contribution to reducing the effective foot length in swing than to providing compliance in stance.