The effect of passive movement of a leg on alpha-motoneurons of the soleus was investigated while the ankle was immobilized. Electrophysiological parameters of the H-reflex were used. Nineteen fully informed volunteers with no history of neurological or internal disease participated in the study. The mean age across all the experiments was 20.9 years. Contributions to the modulation of the soleus H-reflex by hip and knee joint movements were analyzed in two tasks. These were the most general movement methods used in physical therapy. Soleus H-reflexes were measured six times per experiment. Stimulation intensity was set at the 1.1 x M-wave threshold.
Results: 1. In both exercises, H/M decreased as flexion progressed with fast or slow movement. The quadriceps femoris inhibited soleus muscle alpha-motoneurons in both experiments. 2. H/M increased on initiation of extension in the two-joint exercise. In the single-joint exercise, inhibition was retained through the extension phase during both fast and slow movements. Hamstring effects were strong during extension of the leg. 3. In both exercises, the H/M for fast movement was lower than for slow movement at all angles, indicative that H/M decreases with fast movement irrespective of the effects produced by the hip joint.