The purpose of this study is to analyze the kinetic electrical activity of the paralumbar muscles during the trunk flexion-extension cycle.

In this study, we analyzed root mean square(RMS) value form paralumbar muscles to quantify the acivity level during trunk flexion-extension movement in 50 patients with low back pain and control group.

In the control group, RMS value from paralumbar muscles decreases as flexion of the trunk increases, and relaxation of the muscle occurs in the fully flexed posture. In extension of trunk, the pattern of activity is reversed.

However, in 28 patients(56% of all patients), only a partial decrease in myoelectirc activity was seen in full flexion. (i,e, the flexion relaxation phenomenon was absent.)

In addition, the ratio of highest RMS value during flexion and extension(F/E ratio) was higher in patients than in control group(P<0.001).

The results indicate that RMS value recording is a valuable tool in the assessment of dynamic spine functions in patients with low back pain and provides guideline to proper rehabilitative treatment and prevention for low back pain.