Enhancing Seated Stability Using Trunk Support Trainer (TruST)

Dynamic seated trunk control is required during the execution of many everyday tasks. These tasks require an intricate coordination between the head, upper and lower trunk, and the pelvis. Furthermore, reaching beyond the arm's length requires precise joint control and intersegmental coordination. With practice specificity, humans can learn particular motor skills that may be performed across contexts of similar characteristics. As new tasks are explored, human movements are learned and organized by the release and constraint of degrees-of-freedom, and the modulation of joint amplitudes that are specific to the task demands. Thus, by providing seated reach training without foot support that challenges postural control close to and beyond the stability limits or point of stability failure, an individual with an optimal level of trunk assistance could improve postural control by increasing the range of motion of the trunk and expand the boundaries that define the point of stability failure. We have developed a novel cable robotic device, trunk support trainer (TruST), which allows training of seated posture at and beyond an individual's point of stability failure during volitional trunk displacement. This is accomplished by creating a force tunnel to support posture beyond the sitting stability region. The system provides an assist-as-needed force strategy to support the trunk. We conducted a proof-of-concept study with 20 healthy adult subjects (10 experimental and 10 control) to investigate the changes in lower trunk center of mass (COM) displacement and trunk kinematics. Our study supports the hypothesis that a single training session with TruST at and beyond the point of stability failure increases lower trunk COM displacement and increases the lower trunk and pelvic rotation. The findings suggest that this approach may be useful for training patients with neurological and musculoskeletal disorders where children or adults have compromised postural stability.