For the preliminary data to the relaxation training of spasmodic paravertebral muscle in the low back pain sufferers with myofeedback, integrated EMG (full wave rectified and averaged values of the signal amplitudes) of the paravertebral muscles, L₅ & S₁, was done in the low back pain patients (6 persons) and the healthy men (10 persons) at the prone, Taylor's posture and the standing postures.

The results obtained were as follows;

1) In the control group, the intgrated EMG value (iEMG) of the paravertebral muscles, was significantly increased at the standing posture, but at the Taylor's posture there was no significant difference to the prone posture.

2) In the back pain group, iEMG of the paravertebrl muscles, at the site of radiating pain occurred, had no significant difference to the opposite site.

3) In the back pain group, iEMG of the paravertebral muscles was significantly increased at the Taylor's posture as well as standing posture. There was no significant difference between the Taylor's and standing posture.

4) In the back pain group, iEMG of the paravertebral muscles was significantly higher than those in the control group at the Taylor's posture but at the other potures, were there no significant differences to the control group.