Autonomic Nervous System Adaptation to Supernumerary Robotic Finger Use: Coherence Analysis of RR Intervals Before and After Training

Supernumerary robotic fingers (SRFs) are wearable assistive devices, which are increasingly incorporated into robotic rehabilitation programs aimed at restoring upper-limb function and promoting task-specific compensation. Despite growing evidence of SRF efficacy in improving motor performance, limited attention has been given to physiological adaptation and autonomic nervous system (ANS) integration during SRF use. This study investigated phase coherence (PC) and amplitude-weighted phase coherence (AWPC) of RR intervals derived from photoplethysmogram (PPG) as noninvasive biomarkers for autonomic nervous system adaptation during SRF-assisted activities of daily living. Thirty healthy participants completed a baseline (no SRF), pre-training SRF application and post-training SRF use, including rest periods protocol. Drinking water, driving and shape sorting were the functional activities of daily living (ADLs) that had to be completed. The results for PC and AWPC in the low (0.04-0.15) and high (0.15-0.4) frequency bands indicated an overall significant reduction in stress associated with SRF use (p