An accelerometer-based single-arm dynamic stability test for the assessment of the sensorimotor control of the shoulder

The study aimed at designing and validating a variation of the Single-Arm Dynamic Stability test as performed in Open Kinetic Chain for assessing the shoulder's sensorimotor control with the subject lying supine while holding a dumbbell still in one hand with the extended arm. The dumbbell's sway, monitored via a triaxial accelerometer, was modelled as an inverted pendulum pivoted at shoulder level. Twenty college students performed bilateral tests for 30 s using loads of 15 %, 25 %, and 35 % of a reference load determined as the mass measured by a scale placed under the hands during a quadruped position. The test was repeated 30 min and 24 h later. Time- and frequency-domain stabilometric parameters were computed using both the entire 30 s test duration and the first 20 s. ICC analysis revealed that the test as performed at 15 % of the reference load exhibited the highest intra- and inter-day reliability for both sides and durations, while reliability decreased at higher loads. Specifically, Jerk and swayArea exhibited good-to-excellent intra-day reliability (ICC = 0.866–0.947) and moderate-to-good inter-day reliability (ICC = 0.707–0.766), with 30 s test duration. All other stabilometric parameters showed moderate or moderate-to-good reliability (ICC > 0.5). The test provides a reliable, accessible, and ecologically valid assessment of shoulder sensorimotor control, with potential applications in clinical settings.