Hand-held dynamometry strength measures for internal and external rotation demonstrate superior reliability, lower minimal detectable change and higher correlation to isokinetic dynamometry than externally-fixed dynamometry of the shoulder

Objectives: To investigate inter and intra-rater reliability of hand held (HHD) and externally fixed (EFD) dynamometry for shoulder internal (IR) and external rotation (ER) strength and their correlation to isokinetic testing.

Design: Within participant, inter and intra-rater reliability study.

Participants: Twenty active, healthy male and female participants underwent testing by two examiners.

Outcome measures: Intra-class coefficients (ICC), percentage standard error of measurement (%SEM), and percentage minimal detectable change (%MDC) were calculated for inter-rater, intra-day and intra-rater, inter-week reliability. Maximum and average of three repetitions were compared to the isokinetic results at three speeds (60°/sec, 180°/sec, 240°/sec) for both concentric and eccentric contractions.

Results: Inter and intra-tester values demonstrated good to high agreement (HHD, ICC range = 0.89-0.97, %SEM = 4.80-8.60%, %MDC = 13.29-23.70%; EFD, ICC = 0.88-0.96, %SEM = 6.60-11.00%, %MDC = 18.40-30.04%). HHD and EFD showed moderate to very strong correlations to the isokinetic testing (HHD, r = 0.45-0.86; EFD, r = 0.49-0.83).

Conclusions: The results of this study indicate that both EFD and HHD are suitable for clinical practice and research. Hand-held dynamometry is preferred due to its higher intra- and inter-rater reliability and smaller MDC and lower SEM.