Reliability and validity of eccentric strength measurement of the shoulder abductor muscles using a hand-held dynamometer

Abstract

Objectives: To investigate the validity and intrarater and interrater reliability of eccentric strength testing of the shoulder abductors using a hand-held dynamometer (HHD) versus an isokinetic dynamometer. Design: Methodological. Setting: Research laboratory and athletic training room. Participants: Forty-seven asymptomatic shoulders of 25 participants were tested in 2 sessions by 2 physiotherapists. Main outcome measures: Eccentric strength of the shoulder abductors was measured from 120 degrees to 30 degrees scapular plane abduction using the HHD and isokinetic dynamometer. A gyroscope was used to validate the velocity. Spearman's rank correlation coefficients, intraclass correlation coefficient (ICC), standard error of measurement (SEM), and minimal detectable change (MDC) were calculated. Results: The measurement protocol showed excellent intrarater (ICC[3,3] = 0.987, SEM = 2.59 Nm and MDC = 7.18 Nm) and interrater (ICC[3,3] = 0.990, SEM = 2.28 Nm and MDC = 6.32 Nm) reliability. HHD and isokinetic dynamometer measurements were strongly correlated (rho = 0.760, p < .001). Velocities during HDD testing were similar to those of the isokinetic dynamometer (30 degrees/s) (p > .050). Conclusions: Eccentric strength testing of the shoulder abductors using an HHD is a valid and reliable method that can be used for research and clinical purposes when an isokinetic dynamometer cannot be used. (C) 2020 Elsevier Ltd. All rights reserved.