Neuro-mechanical and Clinical Outcome of Stroke Rehabilitation of Ankle Impairments through Passive Stretching and Active Movement Training 1 Genna Waldman, 1 Yi-Ning Wu, 1 Yupeng Ren, 2 Yue Li 3 Liang Wang, 1 Xin Guo, 1,2 Elliot J. Roth, 1,2 Li-Qun Zhang 1 Northwestern University, Chicago, IL, USA 2 Rehabilitation Institute of Chicago, Chicago, IL, USA 3 Illinois Institute of Technology Email: l-zhang@northwestern.edu INTRODUCTION Spasticity, contracture and motor impairment are major sources of disability in neurological disorders including stroke, spinal cord injury, multiple sclerosis, and cerebral palsy [1-2]. Treatment of these pathological conditions presents a constant challenge to the medical rehabilitation community. Physical therapy is important and effective in treating joints with limited mobility, spasticity and/or contracture [2-3]. Manual stretching used in physical therapy may be laborious to the therapists and the outcome is dependent on the experience and the subjective “end feeling” of the therapists. There is a need for an effective and convenient method of therapy for stroke survivors with impaired ankles. The objective of this study is to investigate the neuromuscular/biomechanical changes and clinical outcome in stroke survivors induced by controlled passive stretching and active movement training of the impaired ankle using a portable rehabilitation robot. METHODS Seven stroke survivors are participants in this study (Table 1). The first four subjects have completed the study protocol and the last three are currently going through the training intervention. The study consists of 18 one hour sessions (3 times a week over 6 weeks) using a custom portable ankle rehabilitation robot. Neuromuscular/biomechanical as well as clinical evaluations are done before and after the training. The training sessions includes both passive stretching and active movement training. During each session the subjects will sit with their leg in an extended position (so that gastrocnemius as well as soleus muscles would be stretched) and their foot secured in the footplate of the portable rehabilitation robot (Figure 1). Stretching limits are based on manual measurements of the subject’s range of motion at the beginning of each training session, with extra room allowed for potential improvement through the passive and active movement treatment. The device stretches the ankle safely throughout the range of motion (ROM) to extreme dorsiflexion and plantarflexion until a specified peak resistance torque is reached with the stretching velocity controlled based on the resistance torque (the higher the resistance, the slower the stretching). The ankle is held at the extreme position for a period of time to let stress relaxation occur before it is rotated back to the other extreme position. Figure 1. Experimental Setup. After a period of stretching of about 20 minutes, the subject will use the loosened calf muscles immediately in voluntary movement training for about 30 minutes. They use the ankle rehabilitation robot to play biofeedback computer games, which help motivate them and facilitate motor recovery. On the one hand, if the patients cannot finish the active movement task, the robot will provide