Quantification of lumbar function. Part 1: Isometric and multispeed isokinetic trunk strength measures in sagittal and axial planes in normal subjects.

The goals of this study were to: evaluate the repeatability of a method of measuring trunk strength; measure isometric and isokinetic strength of trunk flexors, extensors and rotators; explore relationships among these muscle groups; and compare a torque to body weight adjustment measure versus lean body weight. One hundred twenty-five normal subjects (62 males, 63 females) were tested using a Cybex prototype trunk extension-flexion system. Sixty-seven subjects (25 males, 42 females) were tested using a prototype torso rotation unit. Fifty were tested on both devices. Results demonstrated that the strength data were reliable, with strength being greatest in extension. The following were also learned-torque output declined slightly with increased speed; extensor-flexor strength remained consistent from 18 to 44 years; extension-flexion ratios exceeded 1.1:1; left to right rotation ratios remained 1:1; there was no significant difference between torque adjusted to body weight or to lean body weight.