Correlation analysis between the surface electromyography and muscle fiber types of the core muscle group in the patients with myofascial pain syndromes

OBJECTIVE To detect the core muscle group in the patients with myofascial pain syndromes(MPS) by using the surface electromyography; to detect the distribution of muscle fiber type by the analysis of the median frequency and the slope of the median frequency. METHODS From October 2017 to March 2018, there were 100 patients with the MPS, including 45 males and 55 females; the average age was 48.5 years old, ranging from 29 to 76 years old. There were 40 cases of left back pain and 60 cases of right back pain. The course of illness was more than 6 months. Another 40 healthy patients without pain in the waist were included in the control group, 20 males and 20 females; the average age was 47.3 years old, ranging from 29 to 76 years old. All the patients had different degrees of back pain and muscle stiffness, which were diagnosed as lumbar fasciitis by clinical and imaging examination. Surface electromyography was used to measure the characteristics of the lumbar core muscles (multifissions, iliocostal muscles, and longest muscle) of the three groups in the Biering-Sorensen testing, such as median frequency(MF) and absolute slope of median frequency (MFs). RESULTS The MF values of the multifidus muscle in the three groups were as follows:the left side of the non-pain group was 133.88±26.61, and the right side was 131.39±29.81; left side of lift side pain group 117.29±10.93, right side 133.70±17.81; in the right pain group, the left side was 131.36±17.37, and the right side was 118.28±13.57. The MF values of the iliocostal muscle in the three groups were:106.94±28.01 on the left side of the non-pain group, 114.68±18.96 on the right side; left side of lift side pain group 93.95±11.17, right side 107.60±27.86; in the right pain group, the left side was 105.93±15.52, and the right side was 97.27±19.27. The MF values of the longest muscle in the three groups were:109.24±26.20 on the left side of the non-pain group, 112.58±17.70 on the right side. Left side of left side pain group 95.58±10.83, right side 108.79±26.39; in the right pain group, the left side was 106.50±17.98, and the right side was 98.20±11.16. The MFs values of the multifidus muscle in the three groups were:0.221±0.109 on the left side of the non-pain group, and 0.259±0.169 on the right side; left side of left side pain group 0.318±0.184, right side 0.210±0.159; in the right pain group, the left side was 0.258±0.169, and the right side was 0.386±0.166. The MFs values of the iliocostal muscles in the three groups were:0.241±0.158 for the left side of the non-pain group, and 0.238±0.128 for the right side. Left side of left side pain group 0.330±0.208, right side 0.252±0.171; in the right side pain group, left side 0.249±0.150, right side 0.343± 0.144. The MFs values of the longest muscle of the three groups were:0.244±0.252 on the left side of the non-pain group, and 0.210±0.128 on the right side; left side of left side pain group 0.348±0.255, right side 0.241±0.224; in the right pain group, the left side was 0.239±0.155, and the right side was 0.334±0.233. There were no statistically significant differences in MF and MFs values of the left and right lumbar multifidus muscle, iliocostal muscle and longest muscle in the non-pain group(P>0.05). MF values of the pain side multifidus muscle, iliocostal muscle and longest muscle in the lumbago group were lower than those in the non-pain group(P<0.05). MFs values of the painful side multifidus muscle, iliocostal muscle and longest muscle in the low back pain group were higher than those in the non-pain group(P<0.05). CONCLUSIONS The muscle fatigue degree of the back muscle in the pain side of patients with MPs is decreased, and the muscle fiber type is dominated by II muscle fiber.