Article

The gastrocnemius and soleus both contribute to the ankle plantarflexor moment
during the mid- and terminal stance phases of gait. The gastrocnemius also
generates a knee flexion moment that may lead to dynamic function that is unique
from the soleus. This study used a muscle stimulation protocol to experimentally
compare the contributions of individual plantarflexors to vertical support,
forward propulsion and center of pressure (CoP) movement during normal gait.
Twenty subjects walked on an instrumented treadmill at self-selected speeds with
stimulating surface electrodes affixed over the medial gastrocnemius and soleus
muscles. Short duration pulse trains (90 ms) were used to stimulate either the
gastrocnemius or soleus at 20% or 30% of the gait cycle (GC) of random strides.
Changes in ground reactions between stimulated and non-stimulated strides were
evaluated to characterize the influence of each muscle on whole body movement
during mid- (stimulation onset at 20% GC) and late (30% GC) stance. The
gastrocnemius and soleus each induced an increase in vertical support and
anterior progression of the CoP in mid-stance. However, late stance gastrocnemius
activity induced forward acceleration, while both mid- and terminal stance soleus
activity induced braking of forward velocity. The results suggested that the
individual plantarflexors exhibit unique functions during normal gait, with the
two muscles having opposite effects on forward propulsion. These empirical
results are important both for enhancing the veracity of models used to predict
muscle function in gait and also clinically as physicians seek to normalize gait
in patients with plantarflexor dysfunction.
CI - Copyright (c) 2013 Elsevier B.V. All rights reserved.

Langue : ANGLAIS