Patterns of inter-joint coordination during a single-limb standing

Past studies have documented contributions of multiple joints in maintaining a single-limb standing, but no reports on patterns of inter-joint coordination. It is also unknown whether such inter-joint coordination, if exists, depends on visual feedback. Eight health young volunteers took part in this study. The inter-joint coordination during a single-limb standing were examined using 3D joint kinematics. There were five testing trials with eyes open (EO) and five trials with eyes close (EC) conditions. During each trial the subject stood on the right leg on an even platform for 20 s while 3D kinematic data was recorded. Recorded data was processed for an "adjusted coefficient of multiple determinations (ACMD)" to evaluate the inter-joint similarities in joint motions. Under both EO and EC conditions moderate to good similarities were found in axial rotation between the ankle and hip joints, and between ankle inversion/eversion and hip axial rotation. This pattern of the inter-joint coordination might be a unique feature of biomechanical configuration of the lower extremity. The significant increases in joint rotations but maintained inter-joint coordination from EO to EC condition may indicate a minimal influence of vision on the inter-joint coordination. Future studies to test patients with pathological conditions in single-limb stance need to examine any alternation/impairment of the inter-joint coordination pattern.