Inter-trial variation in soleus H reflex amplitude for different effort modes, elicited at different test-stimulus intensities, was studied in fifteen healthy subjects. Regardless of test-stimulus intensity, weak isometric plantar-flexion and dorsiflexion at 20% of maximum voluntary contraction caused significant potentiation and depression of the H reflex amplitude. In addition, both facilitation and inhibition of the soleus H reflex was associated with considerable inter-trial variability of the H reflex amplitude that varied proportionally with test-stimulus intensity. As inter-variability of the H reflex was independent of that of M response, the results indicate that: 1) supra-spinal input influences loop-gain fluctuations of the monosynaptic-reflex arc; and 2) smaller test stimuli may be more efficacious for exploration of motoneuronal excitability because of reduction in variability in H reflex amplitude.
|頁（從 - 到）||507-512|
|期刊||Electromyography and Clinical Neurophysiology|
|出版狀態||Published - 2002 12月|
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