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 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.

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