The purpose of this study was to obtain the normative values for variable parameters of lumbar function with the isoinertial triaxial dynamometer in normal subjects and to compare these values with those of the patients with chronic low back pain.

In 82 normal subjects and 27 patients with chronic low back pain, the variable parameters including lumbar range of motion (ROM), maximum isometric torques, and maximum isoinertial velocities were measured with the isoinertial triaxial dynamometer in three axes (rotation, flexion-extension, and lateral flexion). In normal subjects, all parameters except lumbar ROM of all three axes were significantly higher in the male group than the female group. However, other anthropometric variables such as age, height, weight, and body mass index were little correlated with each parameter. Therefore, the normative values were obtained only in consideration of the gender. In patients with chronic low back pain, all parameters except the maximum isometric torques in the female group were significantly lower than those in normal subjects. In addition, the decrease of maximum velocities during the isoinertial exercise was highly correlated to verbal rating scales (VRS) in most axes, especially in the female patient group, but the duration of low back pain was little correlated with the various parameters measured with the isoinertial triaxial dynamometer.

In conclusion, all parameters measured with the isoinertial triaxial dynamometer in all three axes were significantly lower in patients with chronic low back pain than those in normal subjects except maximum isometric torques of female group. It was suggested that maximum isoinertial velocities were more reliable and significant than maximum isometric torques for the objective assessment of chronic low back pain.