Post-stroke Perturbation Training

A novel device will be used to apply controlled mediolateral perturbations to participants' trunk as they walk on a treadmill, requiring reactive responses to avoid a loss of balance. All perturbations will have a duration of 200 ms, and will be applied immediately after onset of the swing phase with either the paretic or non-paretic leg. If in a given training session, a participant does not experience any losses of balance, the perturbation magnitude will be increased in the next training session. Perturbations will begin at 3% body weight (BW), and will progress in increments of 3% BW up to a maximum of 15% BW. The structure of the Reactive perturbation session will be identical to that used for Proactive perturbation training sessions, including overground trials, treadmill trials without perturbations, and Perturbed and Catch trials in which Perturbations are delivered.

A novel device will be used to perturb the relationship between pelvis motion and step width by applying mediolateral forces to participants' legs. Participants will first perform a 3-minute overground walking trial at their self-selected speed, in which they do not interact with the perturbation device. Participants will then perform a 3-minute treadmill walking trial at their self-selected speed, in which they again do not interact with the perturbation device. Participants will then perform a series of alternating 3-minute Perturbed and Catch trials, all at their self-selected speed. For the Perturbed trials, perturbations will be delivered in each step throughout the trial. For the Catch trials, perturbations will cease for the final minute of walking. A total of 5 Perturbed and 5 Catch trials will be performed. Finally, participants will perform a 3-minute overground walking trial at their self-selected speed, in which they do not interact with the perturbation device.