Assessing Changes in Human Gait with a Mobile Tethered Pelvic Assist Device (mTPAD) in Transparent Mode with Hand Holding Conditions.

Robotic gait trainers provide the capability for gait training while adding the application of repeatable forces to specific joints or segments of the user's body. These robotic devices, in principle, should make minimal alterations to the user's natural gait. Hence, the transparency of each device needs to be evaluated. This work explores the effects of walking in a mobile Tethered Pelvic Assist Device (mTPAD) in a zero-force mode. Eight neuro-typical adults walked in three conditions to evaluate changes in their natural gait due to the device and holding its handrails. The changes in spatial and temporal gait parameters and lower limb and arm muscle activations were characterized. Our results showed that walking in mTPAD in a zero-force mode was not significantly different from baseline treadmill walking for all recorded peak muscle activations and gait parameters, highlighting the mTPAD's transparency. When the users hold the device's frame, peak bicep activation increases, and the users take slower, narrower steps. However, frame holding did not significantly alter any lower limb peak muscle activations. This work verifies the transparency of the mTPAD's zero-vertical force controller and isolates changes in the muscle activations and gait patterns caused by holding the device's frame. This investigation can motivate the design and control of other user-propelled robotic gait trainers. This work also allows future studies with mTPAD to separate gait changes caused by force interventions from changes due to holding the device.