Angular movements of the trunk and pelvis when stepping over obstacles of different heights.

This study was performed to investigate the effect of obstacle height on the angular movements of the trunk and pelvis. Seven healthy subjects (all men) participated in the study (age: 22.0 ± 1.2 years; height: 1.73 ± 0.05 m; mass: 69.1 ± 7.9 kg). Subjects were instructed to perform unobstructed level walking and to step over obstacles corresponding to 5%, 10%, and 15% of each subject's height. The video-based WINanalyze 3D motion measurement system was used to measure the three-dimensional (3D) angular movements of the trunk and pelvis. In the frontal and horizontal planes, peak-to-peak amplitudes of trunk rotation developed as the obstacle height increased. However, peak-to-peak amplitudes of pelvic rotation were not significantly different when stepping over obstacles of different heights. The coefficients, which revealed the degree of synchrony of the shoulder and pelvis, showed a trend of decreasing as the obstacle height increased. These results suggest that stepping over obstacles poses a significant challenge to the coordination of the trunk and pelvis. Pelvic rotation is important in adjusting the crossing stride and clearing an obstacle. In coordination with the pelvic motion, the shoulder plays a role in maintaining dynamic equilibrium when stepping over obstacles.