Quantifying Human Autonomy Recovery During Ankle Robot-Assisted Reversal of Foot Drop After Stroke

In this paper, we present a measure to quantify the profile of human autonomy recovery during ankle robot-assisted locomotor training to reverse foot drop after hemiparetic stroke. Underlying this kinetic-based measure is the estimation of the human ankle torque contribution during dynamic (step-by-step) patient-robot interaction, by measuring the device peak torques that meet desired design criteria across gait cycles. As with our previous clinical trials with the ankle robot, we employ an adaptive control approach for a six-week treadmill intervention in chronic stroke patients with well-defined ankle deficits. Here, we provide the first evidence of ankle robot-mediated changes in human autonomy index (HAl) and assess the worthiness of the HAI to predict changes in key volitional ankle neuromotor and whole-body functional gait outcomes. We also propose ways to incorporate the HAl into practice, including a model to customize the duration of robotic therapy for each patient based on minimally acceptable improvements in outcome measures.