Nonlinear analysis of electromyography signals from the deep lumbar multifidus of patients with chronic low back pain / 中华物理医学与康复杂志

ABSTRACT

Objective:To explore any changes in the electromyographic (EMG) signals from the deep lumbar multifidus (DM) of patients with chronic low back pain (cLBP).Methods:Twenty-five cLBP patients formed the cLBP group, while twenty-eight healthy counterparts similar in sex, age and education background were chosen as the control group. EMG signals were recorded during maximum isometric voluntary contraction of the DM. Two-way repeated measures analysis of variance was applied to compare the two groups′ signals′ Lempel-Ziv (LZ) complexity values at rest and during the maximum strength, strength endurance and relaxation stages of contraction. Pearson correlation coefficients were computed relating the LZ complexity to pain duration and intensity, as well as to Oswestry disability index (ODI) values in the cLBP group.Results:The cLBP patients reported a mean symptom duration of 5.96±4.69 years, with an average VAS score of 4.00±1.04 and ODI of 17.12±10.49. They reported greater pain intensity during needle insertions, needle removal, muscle contraction and relaxation than the healthy controls. There were significant differences in LZ complexity among the four stages of contraction with all of the subjects. The LZ complexity was significantly lower in the maximum strength and strength endurance states, but higher in the relaxation after contraction states in the cLBP group. Pain duration was negatively correlated with the nonlinear index of DM during contraction.Conclusion:Continuous pain stimulation will affect the coordinated control of the deep multifidus muscle, leading to decreased control of core muscles via the central nervous system. That provides insight into the mechanisms underlying activation and coordinated control during chronic pain.