In Aim 2, intensive gait training overground and on the treadmill using the device as appropriate will be provided using a randomized, controlled trial (RCT) design. Determination of optimal swing phase and propulsive assistance provided to subjects to maximize treadmill walking velocity (in Aim 1) will be necessary to assess the efficacy of this technique to improve walking function over prolonged LT sessions. Consistent with work from the previous grant cycle12, we will compare the relative improvements in impairments, activity and participation following 1 of 2, 8 -week interventions to improve walking ability post-stroke. Fifty-six (56) subjects will be recruited, stratified based on walking 10 meters \[requiring moderate assistance (subject performing 50-74%), minimal assistance (subject performing greater than 75% of gait but still needing assist), with a gait speed \<0.5m/s without assist, or with gait speed of \>0.5-0.9m/s without assist. Subjects will be randomized to experimental (intensive gait training using aforementioned gait training principles) or control conditions (conventional physical therapy). The test group will receive 40, 40-minute LT sessions during a 60 minute time period over 8 weeks with subjects ambulating on the treadmill, overground, and on stairs. During the first 5 training sessions, LT will take place solely on the treadmill. After that time, half of the sessions will be walking overground and stairs and half on the treadmill. Training will be performed with a target heart rate of 70-80% of heart rate reserve (HRR) and subjective ratings of perceived exertion of 14-17 when patients are on medications to limit heart rate kinetics. Kinematics during LT will be monitored visually to ensure proper foot placement necessary for continuous stepping while maintaining the appropriate intensity, using the device as necessary. The control group will receive conventional physical therapy (receiving at least 3 sessions of physical therapy per week) at the subject's and medical teams' discretion (day rehabilitation, outpatient, or home health). If the subject is not receiving at least 3 sessions of physical therapy per week, control therapy treatments will be provided consistent with recent data detailing the amount of specific physical therapy activities provided during single-session outpatient visits19and published data21 as well as unpublished data from Moore that delineates the number of steps taken per conventional therapy session based on the gait speed of individual (number of steps during training=1500\*gait speed+200). The additional 200 steps were added to this algorithm to allow for individuals who require assist to receive gait training during the sessions. Clinical and quantitative assessment of neuromuscular and cardiopulmonary impairments, limitations in activity and participation, assessment of corticospinal tract (CST) excitability and integrity will be performed prior to training, mid-training, end of 8 week training, and with a 2-6 month follow-up examination. Control group participants will have the option of participating in 4 weeks of intensive gait training (experimental protocol) at the end of the follow up testing and complete one more testing session at the end of those 4 weeks. Primary outcome measures include laboratory and community measures of ambulatory function, including gait speed over short distances, distance walked and gait efficiency during the 6 min walk, and the amount of daily community stepping (using Step Activity Monitors \[SAM\]20), CST excitability measures using transcranial magnetic stimulation (TMS) (optional) and assessment of white matter tract integrity using MRI (optional).
