# Gamification of Upper Limb Rehabilitation in Mixed-Reality Environment
## 2 Related Works  
Conventional therapy for patients with UE joint injuries requires long-term commitments from the patient, active involvement of the therapists, and specialized resources in a controlled environment. In this approach, the patient must perform routine therapeutic exercises that are non-engaging and repetitive. Such tasks without motivation make the patient reluctant to participate in the therapy sessions. In addition to that, the devices used in conventional therapy are expensive and limited to work under the supervision of trained professionals. However, these manual devices lack sensors to record therapy session data to be analyzed. Therefore, the need for cheap home-based tech-assisted therapeutic solutions is an active research domain among researchers [8]. Recent advancements in a gamified approach by Virtual Reality (VR)/Augmented Reality (AR)/Mixed Reality (MR) technology improve UE rehabilitation, overcoming the drawbacks of the conventional counterpart [9]. In this model, a patient can get home-based therapeutic exercises without the continuous assistance of a therapist. The game's combination of natural and virtual objects and real-time interaction with them provide a familiar environment. Moreover, the patient can receive automated guidance and correction from reliable feedback, which ensures motivation and reward-based engagements. From a neurological point of view, stimulation in brain plasticity during gameplay improves motor functions [10]. Continuous state recording ensures progress tracking of the patient and can also be analyzed for other patients. Moreover, unlike manual hardware, the virtual environment can be modified, and challenging in-game activities can be incorporated based on the patient's abilities. As the gamified therapy system is accessible and provides many advantages over the conventional system, ongoing works aim at different tools and techniques to develop such systems. VR-based games for therapy portray a computer-generated environment where the patient can act using the virtual presence of the human-resembling model. AR incorporates the interaction of those virtual objects using smart handheld devices. The latest addition to this lineage is MR technology, where the real-world environment can co-exist with the virtual world, and the communication between the two happens in real-time. These emerging gamified therapy approaches provide a multimedia-based realistic environment for the patient to induce recovery proactively, discover unknown phenomena through exploration, increase willpower to accept challenges and participate in an inclusive environment improving social communication [11]. VR/AR/MR-based games can be classified based on the degree of immersion and commercial availability. Typically, non-immersive VR games are displayed on a computer screen where the patient can interact with the environment differently using simple hardware devices such as a mouse, joysticks, and haptic devices. Contrary to that, AR/MR games are immersive because they combine the virtual and natural worlds with improved sensory outputs. Such systems require big-screen projection, sophisticated head-mounting display, and various sensors to capture the actions [12]. Moreover, VR/AR/MR games come in commercial and open-source domains. Some notable commercially released games are from Microsoft Xbox Kinect, Nintendo Wii, and Sony's Playstation Move. Although proprietary games are developed for healthy people and lack task-specific modifications, existing works examine the efficacy of such games on UE therapy based on randomized controlled trials (RCT) with evaluation measures on different scales [13]. Existing literature shows that work in VR-based UE therapy is an ongoing process for patients with chronic neurological and musculoskeletal diseases, including stroke [14], multiple sclerosis, and cerebral palsy. Non-immersive VR therapy for UE was applied in [15], where the authors used commercial VR-based software MIRA with Kinect sensors.