Abstract: Objective To investigate the patterns of frequency domain indexes of surface electronic signals of adolescent idiopathic scoliosis (AIS) patients' paraspinal muscles by using surface electromyographic (sEMG) techniques .Methods 25 AIS patients enrolled, 7 males, 18 females, ages range from 11 to 21 years old. All of the enrolled patients undertook the Biering Sorensen test(BST) and the object-lifting test, a Finland made type ME3000P sEMG instrument was applied to record the electronic activities of paraspinal muscles(convex /concave) of all subjects, and the frequency domain indexes: median frequency(MF）,mean power frequency(MPF）, zero crossing rate(ZCR）were analyzed.Results The wave amplitudes and scales of paraspinal muscles electronic frequency domain indexes(MF, MPF, ZCR) were lower than the other tested positions when recorded at the zone of apex vertebrae, and MFslope, MPFslope and ZCRslope all showed a linear degressive tendency as the exercise time was extended.Conclusion Paraspinal muscles at the zone of apex vertebrae have low fatigue durabilities and more likely to be exhausted. sEMG ought to be one of the objective examinations used to evaluate the differences of electronic activities of paraspinal muscles(convex /concave) of AIS patients, and may have a promising value in clinical practice.

Key words: surface electromyography, adolescent idiopathic scoliosis, median frequency, mean power frequency, zero crossing rate