Effect of outdoor footwear bending stiffness on metatarsophalangeal joint kinematics, kinetics, and energy balance during level and uphill walking

In outdoor footwear, sole properties must guarantee grip with the ground and support the forefoot without altering the kinematics of the metatarsophalangeal joints (MPJ). The present study aimed to implement an objective measure of shoe bending stiffness and investigate the effect of shoes with different bending stiffness on MPJ kinematics, kinetics, and energy balance during walking. The bending stiffness of four shoes was calculated using a customized flexometer. Then, the influence of each footwear on MPJ biomechanics during level and uphill walking was investigated with a motion capture system and a force plate on 10 healthy subjects. Results showed that MPJ peak dorsiflexion angle, stiffness, and energy balance were affected both by shoe bending stiffness (p<0.001) and walking slope (p<0.001). The findings of the study, which quantify the influence of shoe stiffness on MPJ biomechanics, will be helpful in the design of outdoor footwear.