Investigating the Impact of Virtual Illusions on Upper Limb Motion: Age-Related Differences and Rehabilitation Implications

Virtual Reality (VR) has emerged as a valuable tool in upper limb rehabilitation, offering an engaging and enjoyable user experience. With advancing age, individuals experience diminished motor control, leading to reduced upper limb range of motion. Although rehabilitation exercises can help mitigate this decline, traditional methods often fail to sustain motivation among older adults. In this study, we investigated the impact of eight VR-based visual illusions, varying in direction and magnitude, on upper limb range of motion during a commercially available VR table tennis game. Motion tracking was conducted using OpenCap's markerless system, with sacrum-to-wrist distance measured as an indicator of arm reach. Twenty participants (N = 20), including 10 young adults and 10 older adults, participated in the study. Results revealed a significant increase in sacrum-to-wrist distance in both mediolateral and anteroposterior directions with variations of illusion magnitudes and directions, regardless of age. Additionally, older adults employed a different arm movement strategy compared to younger participants, despite engaging in the same task. These findings demonstrate the effectiveness of VR-based illusions in enhancing range of motion while highlighting age-related movement differences, paving the way for future age-inclusive VR rehabilitation interventions.