Age and height effects on the center of mass and center of pressure inclination angles during obstacle-crossing.

Tripping over obstacles has been reported as one of the most frequent causes of falls in the elderly. Maintenance of the body's balance and precise swing foot control is essential for successful obstacle-crossing. The aim of this study was thus to investigate the height and age effects on the center of mass (COM) and center of pressure (COP) inclination angles and angular velocities during obstacle-crossing. Ten healthy young and 15 healthy older adults were recruited to walk and cross obstacles of heights of 10%, 20% and 30% of their leg lengths. The COM and COP position data were calculated using data measured from a three-dimensional (3D) motion analysis system and forceplates. Smaller medial COM-COP inclination angles were found in the older group, suggesting that the neuromusculoskeletal system may have more room to control the swing foot with sufficient foot clearance. Decreased inclination angles with increasing obstacle height suggest that the subjects tended to keep their COM position close to the COP position to increase the body's stability. Greater anterior inclination angular velocities were found in the older group to maintain the same inclination angles as the young. Not only inclination angles, but also COM-COP angular velocity, were useful for assessing one's ability to control the body's dynamic stability.