Reliability of isokinetic trunk muscle strength measurement

Objective: To determine the intrarater and interrater reliability of reciprocal concentric trunk flexion and extension peak torque values at different angular velocities using the Cybex NORM isokinetic dynamometer. Design: Trunk flexor and extensor muscles of 15 healthy subjects were assessed at 60degrees/sec and 90degrees/sec angular velocities. Each subject was tested by two physicians three times, with at least 48 hr between test sessions. Intraclass correlation coefficients were used to determine the intrarater and interrater reliability of the reciprocal concentric trunk flexion and extension peak torques at 60degrees/sec and 90degrees/sec angular velocities. Results: For intrarater reliability intraclass correlation coefficients for trunk flexion, peak torque values ranged from 0.89 to 0.95; for the extensors, values ranged from 0.80 to 0.92. The intraclass correlation coefficient values for interrater reliability were also found to be highly reliable, and peak torque values demonstrated intraclass correlation coefficients values that ranged from 0.95 to 0.98. Conclusions: Reciprocal concentric trunk flexion and extension peak torque measurements at 60degrees/sec and 90degrees/sec angular velocities had a high intrarater and interrater reliability with the Cybex NORM isokinetic dynamometer in healthy subjects.