Muscle Coordination During an Endurance Walking Task With Elbow Exosuit Assistance

Exosuits have the potential to support human performance during daily and rehabilitation activities. Understanding how neuromuscular coordination adapts in response to external assistance is essential to designing assistive devices and control strategies that interact effectively with the human motor system. In this work, we investigate muscle synergies and networks in ten healthy adults performing an isometric load-carrying task during treadmill walking, assisted by a hybrid soft-rigid elbow exosuit. Comparison between assisted and unassisted conditions showed that, although the overall network topology remained stable across conditions, the exosuit selectively altered local connectivity by reducing synchronization among antagonist muscles. Furthermore, despite high similarity in the global synergy structure between conditions, a clear shift emerged from a deltoid-dominated to a triceps-dominated synergy when the exosuit was used. This suggests a task-dependent redistribution of coordination strategies, along with an adaptive modulation of muscle contributions under the assisted conditions. These results illustrate the value of combining temporal and frequency-domain analyses to characterize the neuromuscular adaptations occurring during assisted movement. The findings indicate that hybrid exosuit assistance induces specific and interpretable adjustments in coordination patterns while preserving the global organization of motor control. This integrated analytical framework offers a meaningful foundation for the development of assistive exosuits, whose control strategies are informed by the organization of neuromuscular coordination and capable of supporting more efficient and coordinated upper-limb behavior. In the rehabilitation realm, establishing this quantitative baseline of healthy neuromuscular adaptation provides a necessary framework for future applications, wherein such exosuits might be used to encourage physiological coordination without imposing maladaptive patterns for the sake of a suitable behavior for clinical recovery.