Test-retest reliability of kinematic and EEG low-beta spectral features in a robot-based arm movement task

Objective.Low-beta (Lβ, 13-20 Hz) power plays a key role in upper-limb motor control and afferent processing, making it a strong candidate for a neurophysiological biomarker. We investigate the test-retest reliability of Lβpower and kinematic features from a robotic task over extended intervals between sessions to assess its potential for tracking longitudinal changes in sensorimotor function.Approach.We designed and optimized a testing protocol to evaluate Lβpower and kinematic features (maximal and mean speed, reaction time, and movement duration) in ten right-handed healthy individuals that performed a planar center-out task using a robotic device and EEG for data collection. The task was performed with both hands, and the experiment was repeated approximately 40 days later under similar conditions, to resemble real-life intervention periods. We first characterized the selected features within the task context for each session, then assessed intersession agreement, the test-retest reliability (Intraclass Correlation Coefficient, ICC), and established threshold values for meaningful changes in Lβpower using Bland-Altman plots and repeatability coefficients.Main Results.Lβpower showed the expected contralateral reduction during movement preparation and onset. Both Lβpower and kinematic features exhibited good to excellent test-retest reliability (ICC > 0.8), displaying no significant intersession differences. Kinematic results align with prior literature, reinforcing the robustness of these measures in tracking motor performance over time. Changes in Lβpower between sessions exceeding 11.4% for right-arm and 16.5% for left-arm movements reflect meaningful intersession differences.Significance.This study provides evidence that Lβpower remains stable over extended intersession intervals comparable to rehabilitation timelines. The strong reliability of both Lβpower and kinematic features supports their use in monitoring upper-extremity sensorimotor function longitudinally, with Lβpower emerging as a promising biomarker for tracking therapeutic outcomes, postulating it as a reliable feature for long-term applications.