Article

The purpose of this study was to better understand phase differences in the
previously shown reorganization of elevation angles for obstacle avoidance and to
relate them to active and passive energetic contributions at proximal lower limb
joints. Ten healthy young adults stepped over obstacles of different heights. The
fundamental harmonics representing elevation angles of the thigh and shank
segments, their relative phase relationship as well as joint and muscle
mechanical power and related work at the hip and knee joints were calculated. As
higher obstacles were cleared, phase shifts between the thigh and shank increased
due to a greater lead by the thigh for the leading limb and a greater lag by the
shank for the trailing limb. While kinematic patterns were relatively constant,
mechanical work differed greatly with passive energy transfer from the shank to
the thigh during mid-swing dominating in the leading limb, but passive energy
transfer from the shank to the thigh segment during toe-off coupled with active
hip flexor generation in the trailing limb. Shank elevation angle waveform shifts
were related to active knee flexor power in both limbs. However, different power
bursts appeared to be related to thigh elevation waveform shifts in the leading
(shank to thigh passive transfer offset) and trailing (active hip flexor offset)
limbs. These results suggest limb specific temporal organization and underlying
energetic patterns to realize thigh-shank phase shifts necessary for obstacle
avoidance further supporting the theory of independent bilateral control.
CI - Copyright (c) 2012 Elsevier B.V. All rights reserved.

Langue : ANGLAIS