Effects of trunk position change on tibialis posterior motor evoked potential and H wave

Abstract

The purpose of the present study was to examine the effect of changes in the trunk position on the H-wave and motor evoked potential MEP) of the tibialis posterior TP) muscle in healthy subjects, and clarify the necessity of postural control for the treatment of spastic clubfoot in stroke patients. The participants were 13 healthy people 6 men, mean age 21.6±1.3 years). The following measurements were obtained with the participants in trunk flexion or trunk extension in the sitting position. The electromyography reaction time of ankle dorsiflexion as well as the H-wave and MEP of the TP were measured. The effect of the trunk position on each measured value was determined. When the tibialis anterior TA) muscle was at 5% and 20% of the maximum voluntary contraction MVC), the H wave of the TP was significantly lower in the trunk extended position than in the trunk flexed position. There was no significant difference in the MEP during the different trunk positions at 5% and 20%MVC of the TA. However, under the condition of imaging 20%MVC of the TA, the MEP was significantly higher in the trunk extension position. It was revealed that the spinal reflex of the TP was suppressed by maintaining trunk extension. Moreover, it was suggested that excitability changes in the primary motor cortex of the TP might be involved in this process.