Changes in the activity of spinal reflex circuit induced by different sensory inputs: comparison between electrical nerve stimulation and vibratory muscle stimulation

Abstract

The main aim of this research is to investigate whether electrical nerve stimulation or vibratory muscle stimulation differently affect the activity of spinal reflex circuits. We measured soleus H-reflex in eleven healthy subjects. The subjects received electrical nerve stimulation and vibratory muscle stimulation for 15 minutes. Electrical stimulation was applied on common peroneal nerve every 1sec (100 Hz-5 train) at motor threshold intensity of tibialis anterior muscle. Vibratory stimulation was applied over muscle belly of tibialis anterior at 100 Hz (2 mm stroke). The degree of reciprocal Ia inhibition, presynaptic inhibition, Hmax/Mmax were assessed before, immediately after, 15 minutes after and 30 minutes after of the intervention. The degree of reciprocal Ia inhibition significantly increased at the end of electrical nerve stimulation. On the other hand, Hmax/Mmax significantly decreased after vibratory muscle stimulation, and it remained for 15 minutes. Presynaptic inhibition did not show any changes after electrical nerve stimulation or vibratory muscle stimulation. Our results suggested that electrical nerve stimulation and vibratory muscle stimulation have different effects on spinal reflex circuits.