Does applying pulsed electromagnetic field on the lumbopelvic area of postmenopausal women with osteoporosis affect the motoneuron activities of soleus and gastrocnemius muscles? An emphasis on the H-reflex recruitment curve changes

Applying Pulsed Electromagnetic Field (PEMF) on the primary osteoporotic women have been effective in increasing the bone synthesis biomarkers and decreasing of the amplitude and velocity of center of pressure. In the present study, in order to investigate the possible effect of PEMF on the neuromuscular responses, the acute effect of PEMF on the lumbopelvic area in the postmenopausal women with Osteoporosis was studied by recording the soleus and gastrocnemius recruitment curves.
For investigating the acute effect of PEMF, 22 postmenopausal women with osteoporosis (age 48-65) voluntarily entered in the study and randomly participated in two separately sessions applying PEMF and placebo (magnet device off). PEMF was applied on the lumbopelvic area with frequency of 30Hz and intensity of 40G for 45 min. One-week interval was considered between placebo and PEMF sessions. Before and after each session, H- reflex recruitment curve was recorded for soleus and gastrocnemius muscles and then amplitude, intensity of stimulation and latency of threshold, maximum and final H-reflex were determined.
After application of 45 min PEMF, the mean stimulus intensity for recording of initial H-reflex was decreased significantly, in soleus and gastrocnemius muscles (0.48 and 0.55 mA respectively). The latency of this H threshold was decreased significantly also in both muscles (2.01 and 1.67 ms, respectively). The peak to peak amplitude of maximum H response increased significantly, in both muscles compared to the placebo session (p Immediately after applying of PEMF, facilitation in H-reflex response was observed in both soleus and gastrocnemius as a slow and fast twitch muscle. In both muscles, after applying PEMF, recruitment curves shifted to the left side by decreasing the stimulus intensity of initial and maximum H-responses and also their latencies. Conlusivly, this may be caused by the facilitation in the activities of alpha motoneurons in the spinal cord level.