Abstract
There continues to be a need to establish the reliability of repeated measurements of muscle performance in order to compare client strength and endurance measurements with baseline performance and normative data. This study reports on the reliability of concentric isokinetic peak torque, average power, and best work measurements when repeated at three different facilities following the same protocols using the Cybex Liftask (LT), the Trunk Extension/Flexion (TEF), and the Trunk Rotation (TR) isokinetic dynamometers. Ten healthy volunteers 30–48 years of age were assigned a random testing order at each of three facilities after site order was randomly determined. Performance on the LT was tested at the linear velocities of 18 inches/sec, 24 inches/sec, and 36 inches/sec; the TEF at angular velocities of 60 deg/sec, 90 deg/sec, and 120 deg/sec; and the TR at angular velocities of 60 deg/sec, 120 deg/sec, and 180 deg/sec. Lifting was assessed and test-retest reliability was calculated using the intraclass correlation coefficients (ICC) at each velocity with each ICC tested for significance using the paired Wilcoxon test for the LT data, and the Kruskall Wallis test for the TEF and the TR data. No statistically significant differences in peak forceitorque, average power, total work (LT), or best work (TEF and TR) were found between the three testing sites. The ICCs ranged from 0.91 to 0.98 for the LT, 0.88 to 0.93 for the TEF, and 0.94 to 0.98 for the TR. The reliability of the angle of peak force, total work, endurance ratio, and recovery ratio were more variable, ranging from 0.43 to 0.99. Given the consistency of the isokinetic measurements of peak torque, average power, and best work taken with the Cybex back systems, physical therapists could collaborate to generate normative data and conduct clinical research across mUltiple sites as long as the same test protocols were followed and the same model equipment was used.