Article

The aim of the study was to verify whether heel kinematics, ground reaction
forces and electromyography (EMG) during walking are affected when anticipating
slips in anterior-posterior (AP) and medial-lateral directions (ML). Eight
healthy men walked through a 7-m walkway, stepping on a robotic force platform.
Initially, baseline (BASE) gait mechanics were assessed with the platform at
rest. Subsequently, two sets of randomized perturbations (10-cm translations with
at different platform movement velocities) in the AP and ML direction were
applied. Perturbations were interspersed with unperturbed walking (i.e.,
catch-trials C-AP and C-ML). Heel accelerations, ground reaction forces and
activities from the perturbed leg and trunk muscles were analyzed. EMG was
analysed in four epochs: PRE (-100 ms to heel strike [HS]), EARLY (HS to 150 ms
after HS), MID (150-300 ms after HS) and LATE (300 ms to toe-off). Comparisons
were made between BASE, C-AP and C-ML. The first peak of the vertical force
component (Fz) was decreased for C-AP and C-ML (p<0.05) but no changes were found
for braking and propulsion impulses. EMG showed effects of expected slips on
tibialis anterior, gastrocnemius lateralis, soleus and peroneus longus,
especially for EARLY and MID epochs, with direction-specific increases in
activity. In conclusion, expected slips in different directions determine only
marginal changes in terms of kinetics and heel kinematics, but selective
activation after HS indicates that direction-dependent strategies are adopted
when anticipating perturbations.
CI - Copyright (c) 2012 Elsevier B.V. All rights reserved.

Langue : ANGLAIS