The purpose of this study was to investigate the pattern of lumbarmuscle fatigue at spinal level during repeated dynamic trunk flexion andextension exercise in chronic low-back pain (CLBP) patients and incontrol subjects without back pain. The authors used a lumbar extensionmachine which is designed to isolate lumbar extension functions. Theelectromyogram (EMG) signal from erector spinae muscles at lumbar 1(L1), L3 and L5 spinal level was detected by surface electrodes.Subjects were required to perform one set of variable resistance lumbarextensions through a 72° range of motion (ROM) with a weight loadthat allowed 13 repetitions of fatigue contraction. Median frequency(MF) of the EMG power spectrum was analyzed to compare fatigue. Theexperimental results indicated: (1) each lumbar muscle has acharacteristic initial MF (IMF); (2) the IMF of each lumbar level showedno significant difference between the CLBP and control groups; (3) therewere significant differences in the decreasing ratio of MF between L1,L3 and L5 in both groups; (4) the decreasing ratio of MF at L5 in theCLBP group was significantly higher than the control group
展开▼
