A Neck Orthosis with Multi-Directional Stiffness for Resistance Training.

Neck pain is a common condition that affects the general population and burdens the health system. Physical therapy is widely accepted as the most effective approach for addressing this condition but there is no consensus on which set of exercises give optimal results. In this context, mobile neck orthosis can potentially expand the number of exercise treatments as they provide multilateral support in contrast to traditional unilateral exercises. In this regard, a passive system of adjustable stiffness is a practical solution that does not require complex control strategies to regulate the load. Considering this, this work proposes a novel passive orthosis for neck exercises involving cervical rotation and flexion. Firstly, the actuation concept is explained along with the relevant parameters that affect the system's stiffness. Then, a user experiment with volunteers with no clinical conditions was carried out to quantify muscle effort changes using the device with different stiffness configurations. The results showed significant changes for all movements. Particularly, similar muscle activation to traditional therapies was found during cervical rotations.