Ankle Robotics Training After Stroke

Veterans and other Americans who survive stroke often face disabling motor impairments that impede performance of activities of daily living and limit free-living activity. Prominent among these are diminished walking and balance functions, which not only foster a sedentary lifestyle and physical deconditioning, but also increase the risk of injuries due to falls. Recent research has demonstrated how motor learning based interventions can modify brain activity and improve motor functions in persons with stroke. Now there is a major research opportunity to advance the effectiveness of these interventions by applying new robotics technologies to improve control of essential functions such as gait and balance. One critical area for performance of walking and standing balance is the control of the ankles, as they are a major conduit of mechanical power in gait and also modulate torques affecting the motion of the whole body center of mass when balancing. Thus the current proposal is designed to investigate two approaches for using an impedance controlled ankle robot to improve gait and balance among stroke survivors with chronic lower extremity weakness. One approach uses the ankle robot in a seated visuomotor training program that focuses has subjects play video games with the weaker ankle to improve paretic ankle motor control that may carry over to gait and balance functions. The other approach uses task-specific gait training by integrating use of the ankle robot during treadmill exercise training to assess effects on the same functions. The effectiveness of both robotics approaches will be compared to that of a treadmill exercise program without robotics.

Veterans and other Americans who survive stroke often face disabling motor impairments that impede performance of activities of daily living and limit free-living activity. Prominent among these are diminished locomotor function and impaired balance that not only foster a sedentary lifestyle and physical deconditioning, but also increase the risk injuries due to falls. Recent research has demonstrated how motor learning based interventions can modify brain activity and improve motor functions in persons with stroke. Now there is a major research opportunity to advance the effectiveness of these interventions by applying new robotics technologies to improve neuromotor control of essential functions such as gait and balance. One critical area for performance of walking and standing balance is the control of the ankles, as they are a major conduit of mechanical power in gait and also modulate torques affecting the motion of the whole body center of mass when balancing. Thus the current proposal is designed to investigate two approaches for using an impedance controlled ankle robot to improve gait and balance function among stroke survivors with chronic lower extremity hemiparesis. One approach uses the ankle robot in a seated visuomotor training program that focuses on improving paretic ankle motor control that may transfer to gait and balance functions. The other approach follows the dominant rehabilitation paradigm of task-specific training by integrating use of the ankle robot during treadmill exercise training to assess effects on the same outcomes. The effectiveness of both robotics approaches will be compared to that of a treadmill exercise program without robotics.

The study tests the hypothesis that, in persons with chronic lower extremity hemiparesis, 6 weeks of seated ankle robot training will improve paretic ankle motor control with major improvements in standing balance and moderate improvements in gait, whereas the same amount of training on the treadmill with the ankle robot will improve gait function more than balance. Both robot-trained groups will outperform the treadmill only group on balance, while the treadmill + robot group will make the greatest gains in gait and the seated robot group will make some improvement in gait but will show greater gains in ankle motor control and balance.

Aims: In a 6-week intervention (18 sessions) with persons with chronic lower extremity hemiparesis 1) Compare effects of seated visuomotor ankle robot training vs. treadmill + robot training on paretic ankle impairments and motor control; 2) Compare effects of seated-robot vs. treadmill + robot training on functional mobility and balance outcomes; and 3) Compare the effectiveness of both robotics approaches to a standard treadmill exercise protocol of the same duration. This proposal will establish the initial comparative efficacy of two motor learning based approaches using a modular impedance controlled ankle robot and contrast motor control and functional gait and balance outcomes among them. As a pilot study we also will establish initial deficit profiles for users that respond to each intervention across the 6-week period.

Eligibility Criteria:
Inclusion Criteria:

* Ischemic or hemorrhagic stroke \>6 months prior in men or women aged between 18-80 years.
* Clear indications of hemiparetic gait by clinical observation.
* Completed all conventional physical therapy.
* Ability to walk on a treadmill with handrail support.

Exclusion Criteria:

* Cardiac history of (a) unstable angina, (b) recent (less than 3 months) myocardial infarction, congestive heart failure (NYHA category II); (c) hemodynamically significant valvular dysfunction.
* Major clinical depression: CESD score \> 16 and judgment of clinical depression
* Medical History: (a) recent hospitalization (less than 3 months) for severe medical disease, (b) symptomatic peripheral arterial occlusive disease, (c) orthopedic or chronic pain conditions that significantly alter gait function, (d) pulmonary or renal failure (e) active cancer
* History of non-stroke neuromuscular disorder restricting gait.
* Aphasia or cognitive functioning that confounds participation, defined as unable to follow 2 step commands. The Mini Mental State Exam will be administered with a cut-off of less than 23 (less than 17 if education level at or below 8th grade), or judgment of the medical officer.
* Hypertension that is a contraindication for a bout of treadmill training (greater than 160/100 on two assessments).
* Self-report of pregnancy