Comparison of joint space and end point space robotic training modalities for rehabilitation of interjoint coordination in individuals with moderate to severe impairment from chronic stroke.

We have developed a novel robotic modality called Time Independent Functional Training (TIFT) that provides focused retraining of interjoint coordination after stroke. TIFT was implemented on the ARMin III exoskeleton and provides joint space walls that resist movement patterns that are inconsistent with the targeted interjoint coordination pattern. In a single test session, ten moderate to severely impaired individuals with chronic stroke practiced synchronous shoulder abduction and elbow extension in TIFT and also in a comparison mode commonly used in robotic therapy called end point tunnel training (EPTT). In EPTT, error is limited by forces applied to the hand that are normal to the targeted end point trajectory. The completion percentage of the movements was comparable between modes, but the coordination patterns used by subjects differed between modes. In TIFT, subjects performed the targeted pattern of synchronous shoulder abduction and elbow extension, while in EPTT, movements were completed with compensatory strategies that incorporated the flexor synergy (shoulder abduction with elbow flexion) or the extensor synergy (shoulder adduction with elbow extension). There were immediate effects on free movements, with TIFT resulting in larger improvements in interjoint coordination than EPTT. TIFT's ability to elicit normal coordination patterns merits further investigation into the effects of longer duration training.