Article

In this study we investigated the effect of a mechanical perturbation of
unexpected timing during human running. With the use of a powered exoskeleton, we
evoked a dorsiflexion of the right ankle during its swing phase while subjects
ran on a treadmill. The perturbation resulted in an increase of the right ankle
dorsiflexion of at least 5 degrees . The first two as well as the next five steps
after the perturbation were analyzed to observe the possible immediate and late
biomechanical adjustments. In all cases subjects continued to run after the
perturbation. The immediate adjustments were the greatest and the most frequent
when the delay between the right ankle perturbation and the subsequent right foot
touch-down was the shortest. For example, the vertical impact peak force was
strongly modified on the first step after the perturbations and this adjustment
was correlated to a right ankle angle still clearly modified at touch-down. Some
late adjustments were observed in the subsequent steps predominantly occurring
during left steps. Subjects maintained the step length and the step period as
constant as possible by adjusting other step parameters in order to avoid
stumbling and continue running at the speed imposed by the treadmill. To our
knowledge, our experiments are the first to investigate perturbations of
unexpected timing during human running. The results show that humans have a
time-dependent, adapted strategy to maintain their running pattern.
CI - Copyright (c) 2011 Elsevier B.V. All rights reserved.

Langue : ANGLAIS