The late response in the soleus muscle evoked by transcranial magnetic stimulation at the foramen magnum level

In healthy subjects, we studied the late electromyographic response elicited by transcranial magnetic stimulation (TMS) applied at the level of the foramen magnum in the left soleus muscle in an upright and supine posture. The late response at the latency of approximately 40 ms was constantly elicited during both postures. It was elicited during planter flexion, but not dorsi flexion. Additionally, no response appeared in the relaxed muscle. Those behaviours are the same as that of the long-loop reflex (LLR). We believe that the late response may be a long-loop reflex.