In recent years, several multi-user virtual environments (VEs) have been developed to promote motivation and exercise intensity in motor rehabilitation. While competitive VEs have been extensively evaluated, collaborative and competitive rehabilitation VEs have seen relatively little study. Therefore, this article presents an evaluation of a VE for post-stroke arm rehabilitation that mimics everyday kitchen tasks and can be used either solo or collaboratively. Twenty subacute stroke survivors exercised with the VE for four sessions, with the first and third sessions involving solo exercise and the other two involving collaborative exercise. Exercise intensity was measured using inertial sensors while motivation was measured with questionnaires. Results showed high motivation and exercise intensity over all four sessions, and 11 of 20 participants preferred collaborative over solo exercise while only 4 preferred solo exercise. However, there were no differences in motivation, exercise duration, or exercise intensity between solo and collaborative sessions. Thus, we cannot currently claim that collaborative exercises are beneficial for upper limb rehabilitation. Future studies should evaluate other collaborative VE designs in different settings (e.g., at home) and with different participant pairs (e.g., patient-unimpaired) to find effective ways to utilize collaborative exercises in motor rehabilitation.

This paper presents a novel multimodal virtual rehabilitation environment. Its design and implementation are based on principles related to intrinsic motivation and game design. The system consists of visual, acoustic, and haptic modalities. Elements contributing to intrinsic motivation are carefully joined in the three modalities to increase patients' motivation during the long process of rehabilitation. The message in a bottle (MIB) virtual scenario is designed to allow interplay between motor and cognitive challenges in the exercising patient. The user first needs to perform a motor action to receive a cognitive challenge that is finally solved by a second motor action. Visual feedback provides the most relevant information related to the task. Acoustic feedback consists of environmental sounds, music, and spoken instructions or encouraging statements for the patient. The haptic modality generates tactile information related to the environment and provides various modes of assistance for the patient's arm movements. The MIB scenario was evaluated with 16 stroke patients, who rated it positively using the Intrinsic Motivation Inventory questionnaire. Additionally, the MIB scenario seems to elicit higher motivation than a simpler pick-and-place training task.