Impaired posture-dependent modulation of disynaptic reciprocal Ia inhibition in individuals with incomplete spinal cord injury.

Posture influences the strength of spinal reflex circuits in healthy individuals. The purpose of this study was to determine the extent to which sitting and standing posture influences the strength of reciprocal Ia inhibition between ankle flexor and extensor muscles in individuals with incomplete spinal cord injury (SCI). Ten individuals with SCI and 15 healthy individuals participated in the study. Short-latency reciprocal inhibition was measured by conditioning the soleus H-reflex with stimulation of the common peroneal nerve. There was no significant difference in the strength of reciprocal Ia inhibition in sitting and standing positions in individuals with SCI. However, healthy individuals showed increased inhibition in a standing compared to a sitting position. The results suggest an impaired posture-dependent modulation of reciprocal Ia inhibition following SCI.