Article

Stimulation of the femoral nerve in healthy people can facilitate
soleus H-reflex and electromyography (EMG) activity. In stroke patients, such
facilitation of transmission in spinal pathways linking the quadriceps and soleus
muscles is enhanced and related to co-activation of knee and ankle extensors
while sitting and walking. Soleus H-reflex facilitation can be depressed by
vibration of the quadriceps in healthy people, but the effects of such vibration
have never been studied on the abnormal soleus facilitation observed in people
after stroke. OBJECTIVES: To determine whether vibration of the quadriceps can
modify the enhanced heteronymous facilitation of the soleus muscle observed in
people with spastic stroke after femoral nerve stimulation and compare
post-vibration effects on soleus facilitation in control and stroke individuals.
METHODS: Modulation of voluntary soleus EMG activity induced by femoral nerve
stimulation (2xmotor threshold) was assessed before, during and after vibration
of the patellar tendon in 10 healthy controls and 17 stroke participants.
RESULTS: Voluntary soleus EMG activity was facilitated by femoral nerve
stimulation in 4/10 (40%) controls and 11/17 (65%) stroke participants. The level
of facilitation was greater in the stroke than control group. Vibration
significantly reduced early heteronymous facilitation in both groups (50% of
pre-vibration values). However, the delay in recovery of soleus facilitation
after vibration was shorter for the stroke than control group. The control
condition with the vibrator turned off had no effect on the modulation.
CONCLUSIONS: Patellar tendon vibration can reduce the facilitation between knee
and ankle extensors, which suggests effective presynaptic inhibition but
decreased post-activation depression in the lower limb of people after chronic
hemiparetic stroke. Further studies are warranted to determine whether such
vibration could be used to reduce the abnormal extension synergy of knee and
ankle extensors in people after hemiparetic stroke.
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Langue : ANGLAIS