Exploring Mixed-Reality Exergames for Sports Rehabilitation: Design Insights and Evaluation Findings (Preprint)

BACKGROUND Exergaming, involving physically active play, provides a means for motivating and functional training. It may also offer an innovative solution for rehabilitation after sports injuries such as anterior cruciate ligament (ACL) injury. Rehabilitation is lengthy and only partially prepares athletes for the demands of sports. As a result, only 65% of athletes return to the same performance level as before the injury. Exergames specific to ACL rehabilitation are missing. Their unique combination of physical and cognitive challenge may contribute to preparing patients for their return to sports. Collaboration of sport scientists, game designers, and physiotherapists enables comprehensive and user-centered development of an innovative training concept incorporating the needs of both patients and therapists along with scientific evidence. OBJECTIVE This project aimed to develop a specific exergame scenario for sports rehabilitation after ACL injuries. A research-driven, user-centered, iterative approach was followed. The project was structured into four phases: (1) assessment of motor performance during a fitness exergame, (2) investigation and establishment of user requirements, (3) development of a new exergame, and (4) validation of the new exergame. METHODS For assessment of motor performance, lower extremity kinematics during a fitness exergame scenario in the ExerCube were assessed in 24 athletes (6 after ACL injury) using marker-based motion capture. Regarding user requirements, focus groups with physiotherapists and patients were conducted. Development of a new exergame was from the kinematic analysis results and user requirements guided the iterative, interdisciplinary design of a new exergame scenario and movement concept for the ExerCube. For validation, developed exergame scenarios were recurrently evaluated with patient and therapist focus groups and transformed into a final exergame scenario. RESULTS For assessment of motor performance, there was a main effect of exercise in maximal knee valgus, knee internal rotation, and hip flexion with <i>P</i>&lt;.001. Squats showed the lowest knee valgus (4.23°, 95% CI 4.12-4.51) and knee internal rotation angle (3.68°, 95% CI 3.33-4.03). Focus groups revealed that patients want to return to sports as quickly as possible but have concerns about sensory overload during training. Physiotherapists desire a device that allows additional independent training with new therapeutic stimuli. Concerning the development of a new exergame, the movement concept for the new exergame included strength and balance exercises, and a mini-exergame for endurance, reaction, and skill training. Three difficulty levels allow for varying complexity and speed. For validation, focus groups on the newly developed exergame scenarios highlighted their motivational potential, suitability for autonomous use, and the need for therapist-controlled adaptation and integration with conventional tools. CONCLUSIONS The interdisciplinary, evidence-based approach facilitated a systematic development of requirements for an exergame for rehabilitation, ensuring user-centered implementation. A final evaluation confirmed its motivational potential and applicability, leading to its deployment at all ExerCube locations.