NSF Award
1603391
Each year, approximately 800,000 Americans experience a stroke. The majority of these individuals subsequently exhibit reduced functional mobility, a major contributor to decreased quality of life. In part, this reduced mobility is due to gait instability, as reflected by an increased fall risk and an increased fear of falling. Surprisingly, no existing rehabilitation methods have proven able to solve this problem. Even therapies successful at improving gait stability in the elderly have failed in the chronic stroke population. Recent evidence suggests that this failure may be a result of the rehabilitation interventions not targeting the underlying deficits specific to post-stroke gait. In contrast, this project is based on the mechanical requirements of a stable bipedal gait, and specifically targets deficits in the control of mediolateral foot placement often observed after a stroke. This project will develop a novel rehabilitation device that can be used to retrain the typical control strategy used to maintain a stable gait. The resulting device will be used in the development of future rehabilitation interventions to improve gait stability, and thus quality of life, in individuals who have experienced a stroke. Importantly, this device will have the potential to also be applied to the treatment of other clinical populations with an increased fall risk, including individuals with amputations, peripheral neuropathies, or Parkinson's disease. This research takes place at the Medical University of South Carolina, a leading institution in stroke recovery. The strong environment increases the likelihood that the research will be translated into the clinic, as does the structured collaborative involvement of engineers, clinical researchers, and clinicians. This cross-disciplinary collaboration, combined with the recruitment of students from a diverse range of backgrounds, will serve to increase the quality of clinical care experienced by the citizens of South Carolina and beyond.<br/><br/>This project focuses on the optimization of hardware and development of control software for a previously constructed novel elastic force-field. The prototype force-field was developed to address the precise problem that has been revealed by experimental studies in neurologically intact controls and chronic stroke survivors, individuals at an increased risk for falls often do not place their feet in mechanically-appropriate locations. Behavioral experiments with control participants will be used to characterize the interaction between the force-field and its users, and to identify optimal force-field properties to help improve gait stability. First, the relationship between gait stabilization strategy and energetic cost will be characterized for a range of walking speeds and force-field mechanical properties, providing norms for future use. Second, the effects of force-field control strategies designed to reduce foot placement errors will be quantified, revealing if mechanical assistance can have beneficial effects. Finally, the effects of force-field control strategies designed to increase errors in foot placement will be quantified, revealing if beneficial after-effects are produced. In combination, this research will develop and test various force-field control methods, producing a novel rehabilitation device able to train foot placement in the task-specific context of walking. The development of such a device will allow the implementation of gait-training interventions that are currently impossible; no human clinician has the ability to sense step-to-step variations in center of mass motion, and place a patient's foot in an appropriate location within the course of a step. In addition, the novel device will allow the responses to errors in foot placement (a major cause of falls) to be experimentally quantified in a controlled fashion, a capacity that has not previously existed.
