The Role of Muscle Property Changes in Identifying Motor Adaptation Stages for Myoelectric Control

Despite technological advancements in assistive robotics, patients still face considerable challenges in their control, with proficiency varying widely among individuals. While training programs include task-related performance metrics to evaluate individuals' skill levels, these may overlook critical adaptations at the muscle. This study explores neuromuscular adaptations in forearm antagonist muscles during a 3-degree-offreedom myoelectric control task. Participants completed a 45-minute training session and were categorized as rapid learners or plateau learners based on their performance evolution. We then evaluated changes in muscle properties within groups, including stability, antagonistic co-contraction, and neural synchronization. Rapid learners showed lower initial proficiency and improved task performance metrics, with reduced muscle variability and increased co-contraction, suggesting greater movement consistency. In contrast, plateau learners achieved a higher baseline performance with minimal improvements. These individuals reported decreased co-contraction levels and phase locking between antagonistic muscles, indicating task endurance and more fine motor control over time. These findings highlight differences in neuromuscular adaptations among individuals, possibly aiding clinicians in assessing therapy effectiveness.