Abstract Significant functional impairment of the hand is commonly observed following stroke. Robot-assisted training of the hand can help stroke survivors practice complex multi-degrees-of-freedom movements of the hand, but it remains mostly unknown how training conditions affects coordination patterns of the muscles producing hand movements; such changes are critical in restoring hand function of stroke survivors after the training. The overall hypothesis of this proposal is that the adaptation of the hand muscles during assisted training, even for the same type of task, will be significantly affected by the assistance dynamics, sensory feedback, and task condition. The goal of this proposal is to examine the impact of the following three conditions of robot-assisted training on the motor adaptation of the three hand muscle groups (extrinsic extensor, extrinsic flexor, and intrinsic muscles) of stroke survivors. We will investigate: (1) whether two widely-used assistance mechanisms (end- effector vs. exoskeleton) induce different patterns of changes in the extrinsic and intrinsic hand muscle coordination; (2) if sensory modulation of distal and proximal finger joint movements results in different changes in the muscle coordination; and (3) whether the dynamics of the task performed (static vs. dynamic) affect these muscle groups differently when assisted. The proposed study will elucidate the important, but currently not well-understood aspects of robot-assisted training outcomes, i.e., how altered sensorimotor experience affects motor adaptation of stroke survivors at their muscle level. We will use a novel robotic setup and virtual-reality technologies to alter sensorimotor inputs/outputs associated with finger movements of stroke survivors. The results will provide vital information regarding how the key aspects of robot-assisted training (assistance, feedback, and task dynamics) should be designed to effectively restore impaired muscle coordination of the hand. In the long term, these outcomes will lead to therapeutic approaches to restoring hand function of stroke survivors even after the training is completed. 1