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We examined the amplitude modulation of the soleus (Sol) H-reflex during controlled variations of the hip joint angle in 21 healthy adult human subjects. Hip angle variations were imposed separately, or in combination either with stimulation of the plantar skin or with electrical activation of muscle afferents from the medial gastrocnemius (MG) nerve. We found that with subjects in the supine position, flexion of the hip significantly depressed Sol H-reflex excitability, by as much as 50% of control reflex values (Ho) recorded at 10° of hip flexion. Conversely, significant facilitation of the H-reflex was observed when the hip joint was extended (10°), with amplitudes reaching 200±15.3% of Ho. Changes in H-reflex amplitude were also observed during electrical stimulation of either the foot sole or the MG nerve, when stimuli were delivered at different hip angles. Foot sole stimulation resulted in facilitation of the H …