Reliability of a new stabilization device for measurement of muscle strength using a hand-held dynamometer

The hand-held dynamometer (HHD) is a reliable and portable tool for quantitatively assessing muscle strength. However, a number of variables, including the strength of the tester, the adequacy of stabilization, and the selected testing position, can affect the reliability of the device. The objective of the present study was to examine the reproducibility and inter-rater reliability of strength assessments using HHD with and without a stabilization device.

Strength assessments were conducted with and without the stabilization device by two independent raters. Healthy volunteers with no history of musculoskeletal disorders were included in the study. The strength of the shoulder flexion, scapula elevation, knee extension, and hip abduction muscle groups was evaluated using HHD. The reliability of the measurements was evaluated using intra-class correlation (ICC), standard error of measurement, and minimal detectable change.

Fifty-two healthy volunteers (age 21.51 ± 2.02 years) participated in the study. The reproducibility was found to be excellent (ICC = 0.89-0.99). While reliability between the assessors was good to excellent (ICC = 0.85-0.93), reliability between assessors and device was found moderate to good (ICC = 0.48-0.78).

The strength values obtained for all directions of movement with the stabilization device were found to be significantly higher than those obtained without fixation of the HHD. It can be concluded that the data obtained from the assessors and HHD with stabilization device are not comparable. Moreover, the utilization of a stabilization device may serve to enhance the reliability of the measurements by eliminating the rater effect.