Segmental contributions to the center of mass movement in normal gait

Saunders et al.(1953) provided a qualitative description of the contributions to the center-of-mass (CoM) movement. The objective of this work is to analytically quantify and study the kinematic contributions to the CoM movement in gait. A ten-degree-of-freedom anthropomorphic link segment model is used. The choice of segment angles as the generalized coordinates and a subsequent reformulation enabled the decoupling of the expression for CoM position as a summation of the kinematic contributions of individual segments. Using data from literature, the segmental contributions to the CoM displacement are then studied. Results show that the sagittal plane rotation of the shank and thigh of the stance leg are the major contributors to the CoM movement in the vertical and anterior-posterior directions. Additionally, forefoot rolling is seen to be a major contributor to the CoM vertical movement towards the end of the single support phase. In the medio-lateral direction, the frontal plane rotations of the pelvis and the stance leg are seen to be the major contributors. Results validate observations made by other researchers regarding the contributions of the degrees of freedom of the lower limbs to the CoM movement. The methodology can be extended to study asymmetric gait, such as the gait of a prosthesis user, where the properties and kinematics of the prosthetic limb are likely to differ from those of the unaffected side.