Relationship between foot arch deformation characteristics and balance-maintenance mechanism during support phase in running

Abstract

The purpose of this study was to clarify relationship between foot arch deformation characteristics and balance maintenance mechanism during support phase in running. The functional roles of support leg joints were analyzed by quantifying dynamic contributions of the joint torques to the generation of ground reaction force (GRF) and ankle angular acceleration vectors normal to the frontal plane using the equation of whole-body motion. Seven male runners participated in this research and ran at the speed of 5.5m/s. The trajectories of 47 markers attached to the body and the ground reaction force of the support leg were measured with VICON-MX system with a force plate. In addition, the stiffness of the arch was identified during a support phase of a gait for one step. From the magnitude of the arch stiffness, the participants were divided into two groups such as Type L (low arch stiffness) and Type H (high arch stiffness). The results of analyses indicate that 1) the contributions of individual joint axial torques to the horizontal medial-lateral components of the GRF were canceled so as to reduce the component regardless of the type of groups, 2) the contributions of individual joint axial torques to the ankle angular acceleration, whose axis is normal to the frontal plane, were canceled so as to reduce the angular acceleration, 3) the GRF and the angular acceleration were induced by joint torques whose axes are not only normal to frontal plane but also along other directions, and 4) the difference of balance maintenance mechanisms between the groups in the frontal plane maybe due to differences in arch stiffness as well as running forms and COP locations.