Intratester Reliability and Validity of Concentric Measurements Using a New Hand-Held Dynamometer

Objective: To assess the reliability of a new hand-held dynamometer (HHD) to perform concentric measurements, and to determine the agreement between the HHD and the criterion standard isokinetic dynamometer. Design: Elbow flexion concentric measurements were performed on a mechanical arm using the HHD and the isokinetic dynamometer. Setting: Engineering laboratory and university strength-testing facility. Participants: Three patient profiles, differing in range of motion (ROM) and strength, were simulated by a mechanical arm. Interventions: Not applicable. Main Outcome Measures: Peak torque and ROM obtained from concentric elbow flexion profiles. Results: Intratester reliabilities, measured with the intraclass correlation coefficient (ICC1,1), of the peak torque and start and end ROM are excellent for both the HHD (.99, .98, and .99, respectively) and the isokinetic dynamometer (.99 for all 3 variables). The angle of peak torque was rated fair to good in intrareliability for both devices, at .64 (HHD) and .69 (isokinetic dynamometer). Validity, measured within the limits of agreement (LOA) between the 2 devices, was clinically acceptable for peak torque and start ROM, although not for end ROM and angle of peak torque. Conclusions: It is possible to use the new HHD to obtain dynamic measurements of joint motion. Intratester reliability of the HHD is excellent and is in clinical acceptable agreement with the isokinetic dynamometer for peak torque and start ROM. End ROM was, however, not in agreement because of a systematic error in the isokinetic dynamometer measurement for I of the 3 tested profiles. Intratester reliabilities of the angle of peak torque were fair to good for both the HHD and isokinetic dynamometer, but the LOA were not clinically acceptable. Stability of the arm and speed of measurement might be confounding factors in this study.