Placement of a plate under the forefoot in stance: decreasing the excitability of the soleus motoneuron pool.

Abstract

To investigate the effect of the placement of a plate under the sole of the forefoot on the excitability of the soleus motoneuron pool in stance. While eight neurologically intact subjects remained in stance, a square plate (30 x 30 mm), either 3 mm or 6 mm in thickness, was placed under the left medial plantar eminence, under the left lateral plantar eminence, or under the left forefoot sole between the eminences, or a rectangular plate (120 x 30 mm), either 3 mm or 6 mm in thickness, was placed under the left metatarsal heads. To investigate the excitability of the soleus motoneuron pool, the Hmax/Mmax ratio was estimated. Analysis of variance revealed that the region under which the plate was placed had a significant effect and that the thickness of the plate had a nonsignificant effect on the Hmax/Mmax ratio, without significant interaction between the two factors. Post hoc analysis revealed a significant decrease in the Hmax/Mmax ratio when the square plate was placed under the lateral plantar eminence. A square plate placed under the lateral plantar eminence inhibited the excitability of the ipsilateral soleus motoneuron pool in stance. This intervention may be useful for reducing spasticity.