Myo-electric behavior of the trunk muscles during static load holding in healthy subjects and low back pain patients

The purposes of this study were to examine coactivational activities of four trunk muscles in various static holding tasks, and to examine the differences of muscle activation patterns between normal subjects and low back pain (LBP) patients. We used an one-way analysis of variance (anova) with repeated measures to analyze the effect of the knee angles, trunk flexion angles, and loading conditions on the amount of EMG activity. Epidemiologic studies attribute a considerable proportion of the incidence of LBP to lifting-related injuries. The relationship between LBP and trunk muscles integrated electromyography (IEMG) is controversial. Forty volunteer subjects with no experience of LBP and 47 LBP patients recruited from Chung-Gung Memory Hospital participated in this experiment. Surface IEMG signals of four right and left trunk muscles (rectus abdominis, external oblique, erector spinae, and latissimus dorsi) were obtained in static holding tasks. In knee flexion, LBP patients had significant IEMG pattern change than normal subjects. In trunk flexion and loading conditions, normal subjects had significant IEMG pattern change than LBP patients. Trunk muscle groups have different muscle coactivation patterns in functional posture of load holding. Using surface EMG can discriminate LBP patients from normal subjects.