The effect of cutaneous mechanical stimulations of medial plantar surface on the excitability of ipsilateral and contralateral motoneurons

Mechanoreceptors from the foot sole likely contribute in the reflex regulations. Stimulation of these receptors in the medial aspect of the foot is corresponded to the medial plantar nerve divisions in the tibial nerve. Therefore, it was hypothesized that repetitive low threshold afferents stimulation would have an inhibitory effect on the soleus H-reflexes. sixteen normal subjects voluntarily, participated in the study. Subjects were remained in prone position. The Cutaneous Mechanical Pressure (CMP) (equal to 50% of leg and foot weight) was applied to the ipsilateral medial plantar surface by a designed instrument through a square plate (30 x 30 mm). H reflex as an indicator for excitability of motoneurones was bilaterally elicited before and after the application of the CMP. The amplitude of H reflex and H/M ratio showed significant differences before and after the Ipsilateral CMP stimulation of the medial side of the foot (p<0.05); furthermore, the latency of H reflex was also increased (p<0.05). In addition, the effect of CMP stimulation of the IPS stimulation showed more difference than the Contralateral side. The results highlights the modulatory effects of natural stimulation of cutaneous afferents on excitability of Ipsilateral and contralateral motoneurones. This in respect may have practical application in the management of muscle tone disorders in brain and spinal cord injuries.