Objective: To know if electro-magnetic stimulation can induce the contraction of gluteus medius and minimus muscles, and to compare pain induced by electro-magnetic stimulation of the gluteal muscles with that induced by transcutaneous neuromuscular electrical stimulation (NMES). Method: Two different intensity of transcutaneous NMES (40 mA, 60 mA) and electro-magnetic stimulation (60%, 100%) were applied to the left buttock of 15 healthy male volunteers in random order. The ultrasound images of gluteal muscles and visual analog scale (VAS) of pain were obtained three times at each type of stimulation. The grade of muscle contraction and the VAS score of each type of stimulation were compared. Results: At maximal stimulation intensity of our equipments, the mean VAS score was lower (p=0.012) in electro-magnetic stimulation than in transcutaneous NMES, and the grade of gluteus minimus contraction was higher (p=0.035) in electro-magnetic stimulation than in transcutaneous NMES. When the mean VAS scores at the same grade of contraction were compared, the VAS scores of electro-magnetic were lower than transcutaneous NMES in both gluteus medius (3.92±1.79 vs. 5.35±2.98, p=0.033) and minimus (4.12±1.85 vs. 5.69±3.00, p=0.046). Conclusion: Electro-magnetic stimulation induced the contraction of gluteus medius and minimus muscles with less pain than electrical stimulation for the same amount of muscle contraction. These results suggest that electro-magnetic stimulation can replace transcutaneous NMES in deep, large muscles such as gluteal muscles. (J Korean Acad Rehab Med 2008; 32: 417-423)
