Isokinetic measurements of trunk extension and flexion performance collected with the biodex clinical data station.

The purposes of the two experiments presently reported were to determine a) the relationship between subject-dynamometer axis alignment and isokinetic trunk extension-flexion performance and b) the effects of short-term acclimation to the isokinetic dynamometer on the magnitude of isokinetic trunk extension-flexion variables for low back pain and asymptomatic subjects. In the first study, three anatomic landmarks were selected for fixed axis alignment, the anterior superior iliac spine, the femoral greater trochanter, and the posterior superior iliac spine. Ten healthy women performed five reciprocal maximal effort, 100 degrees , concentric contraction trunk extension-flexion cycles at three isokinetic speeds (60, 120, 180 degrees /sec) for each of three subject-dynamometer configurations. Peak torque and the trunk angle at which peak torque occurred for both trunk extension and flexion were analyzed. A 3 x 3 analysis of variance did not provide definitive statistical evidence of the superiority of one alignment over the others. The data generated with the anterior superior iliac spine alignment, however, was more consistent than others relative to expected speed-torque relationships and was associated with the overall smallest variability of the data. In the second study, 8 healthy men and 10 men with a history of low back pain were studied with a within-session, test-retest protocol. The peak torque and total mechanical work for trunk flexion and trunk extension were analyzed. As a group, the low back pain subjects demonstrated universal and, in some cases, large performance improvement (>20%) at the retest. The results of the first study suggest that subject-dynamometer alignment using the anterior superior iliac spine is justifiable. Based upon the results of the second study it was concluded that a clinically relevant measure of sagittal plane isokinetic trunk flexion and extension function for low back pain patients should be collected using a test-retest protocol. J Orthop Sports Phys Ther 1990;11(12):590-598.