Motion of the whole body's center of mass when stepping over obstacles of different heights

Tripping over obstacles and imbalance during gait were reported as two of t he most common causes of falls in the elderly. Imbalance of the whole body during obstacle crossing may cause inappropriate movement of the lower extr emities and result in foot-obstacle contact. Thus, this study was performed to investigate the effect of obstacle height on the motion of the whole bo dy's center of mass (COM) and its interaction with the center of pressure ( COP) of the stance foot while negotiating obstacles. Six healthy young adul ts were instructed to perform unobstructed level walking and to step over o bstacles of heights corresponding to 7.5, 5, 10, and 15% of the subject's h eight, all at a comfortable self-selected speed while walking barefoot. A 1 3-link biomechanical model of the human body was used to compute the kinema tics of the whole body's COM. Stepping over the higher obstacles resulted i n significantly greater ranges of motion of the COM in the anterior-posteri or and vertical directions, a greater velocity of the COM in the vertical d irection, and a greater anterior-posterior distance between the COhI and CO P. In contrast, the motion of the COM in the medial-lateral direction was l ess likely to be affected when negotiating obstacles of different heights. (C) 2001 Elsevier Science B.V. All rights reserved.