An Electromyography Study of Acute Low Back Pain

摘要

This paper presents the results of a laboratory investigation to determine the effect of acute low back pain on electromyography amplitude and frequency parameters. Ten (10) subjects, 5 normal and 5 acute low back pain patients,participated in the study. The test protocol involved (a) determination of maximum voluntary contraction (MVC) (b) after a short rest period of 2 minutes, subjects were asked to perform randomised back muscle contractions at 20,40,60 and 80 percent of MVC values for 30 seconds. EMG was recorded from 6 lumbar muscle sites (L1, L2 and L5, both Right and Left). EMG signals were processed and analysed for RMS and median frequency (MF). Two sets of parameters: (a) contralateral ratios (right/left) of RMS and MF values (b) ipsilateral ratios of RMS and MF values for sites L1,L2 and L5 were determined. The results of the study showed that there were differences in EMG signal characteristics between acute LBP (ALBP) and normal subjects. With respect to contralateral ratio parameters, it was found that the average RMS values were higher at L1 for ALBP patients as compared to pain-free subjects. At muscle site L5, the average RMS (rL5/lL5) values,where 'r' and ' 1' represent right and left sides, did not show much difference. Median frequency (right/left) at L1 was found to be lower for ALBP patients compared to pain free subjects. The results of ipsilateral ratio parameters were found to be more consistent than contralateral ratios. In general, ALBP subjects had higher MF ratio values for both right and left sides. The results also showed that the ipsilateral RMS ratio values were higher in ALBP subjects than in normal subjects.