Article

Motor output in activities such as walking and hopping is suggested to be
mediated neurally by purported stretch reflex augmentation of muscle output.
Reflex EMG activity during these tasks has been frequently investigated in the
soleus muscle; with alterations in reflex amplitude being associated with changes
in hip joint angle/phase of the gait cycle. Previous work has focussed on reflex
activity induced by an artificial perturbation or by induction of H-reflexes. As
such, it is currently unknown if stretch reflex activity induced intrinsically
(as part of the task) is modulated by changes in hip joint angle. This study
investigated whether hip joint angle modulated reflex EMG 'burst' activity during
a hopping task performed on a custom-built partially reclined sleigh. Ten
subjects participated; EMG and kinematic data (VICON motor capture system) was
collected for each hop cycle. Participants completed 5 sets of 30s of self-paced
hopping in (1) hip neutral and (2) hip 60 degrees flexion conditions. There was
no difference in EMG 'burst' activity or in sagittal plane kinematics
(knee/ankle) in the hopping task between the two conditions. The results indicate
that during a functional task such as hopping, changes in hip angle do not alter
the stretch reflex-like activity associated with landing.
CI - Copyright (c) 2013 Elsevier B.V. All rights reserved.

Langue : ANGLAIS