An electromyographic investigation of postural fatigue in low back pain--a preliminary study
Jayasinghe, W.J.; Harding, R.H.; Anderson, J.A.; Sweetman, B.J.
Electromyography and Clinical Neurophysiology 18(3-4): 191-198
1978
ISSN/ISBN: 0301-150X PMID: 151622 Document Number: 135815
An electromyographic (EMG) investigation of postural fatigue in low back pain was carried out in the back pain clinic with 11 volunteer subjects aged 15-67 yr. Seven subjects in the study were clinically diagnosed as having recent low back pain and the remaining 4 were controls with no history of low back pain. Two pairs of Ag-AgC1 surface electrodes were attached on left and right sacrospinalis muscles in each subject at L4 and L5 levels. With each subject standing erect EMG recordings were obtained on 2 channels alternating in each minute from left to right up to 6 min. The recorded data were subsequently digitized and analyzed by means of a small digital computer (Hewlet-Packard Signal Analyer). The EMG waveforms were quantified by computing the amplitude variance or mean square value. In addition the power spectrum analysis on initial examination showed the major energy to be distributed in the bands 20-250(Hz). This range was arbitarily divided into low (20-75); medium (76-150); and high (151-255) Hz frequency bands and total EMG and the percentage in each band was computed. The results of the waveform analysis show a general pattern in low back pain patients which depict an increase in the mean square value of EMG in relation to the time of erect standing. The control group as a whole show a definite increase in EMG with time. The experimental results support the case for muscle weakness or fatigue associated with low back pain.