Comparison of trunk strength measurements between two different isokinetic devices used at clinical settings

Intradevice reliability of isokinetic trunk strength measurements has been studied frequently, but no evidence is available on interdevice reliability. This motivated the present study, in which two isokinetic devices, the Ariel 5000 and Lido Multi-Joint II, were compared in a sample of 41 subjects (20 healthy and 21 low back pain subjects). The measurements were made in a random order with both machines. The results showed that the two isokinetic machines gave quite different results in trunk flexion-extension strength measurements. A statistically significant difference was present in the average peak torques between the two devices, with the exception of flexion at low angular velocity (60 degrees/s), and the correlations between the two measurements were low. The results were assumed to be more of a reflection of the interdevice variations (hardware and software, attachment of the subject) than of learning effects or other phenomena. We conclude that isokinetic trunk-muscle strength test results with the Ariel and Lido are device specific, and one cannot automatically compare results obtained from different devices with each other.