H-Reflexes during a Motor Skill Acquisition Task

Abstract

H-reflex amplitudes were studied during the acquisition of a motor skill involving coordinated isometric plantar-flexion at the ankle joints as subjects learned to trace a triangular pattern on an oscilloscope screen by controlling plantar-flexion torque applied against load cells. Torque feedback was presented on a subject oscilloscope with the right foot controlling a vertical cursor and the left foot a horizontal cursor. Eleven subjects reached criterion performance. H-reflexes were recorded from the right soleus and timed to the initiation of soleus muscle activity to plantarflex the foot. Average time to complete one trial decreased from 9 sec. in the prelearning block to 4 sec. postlearning. No single learning strategy was evident as subjects varied widely in their levels of H-reflex amplitude, but during postlearning, H-reflex amplitude became consistent within subjects as tracing performance became faster and accurate.