Sustaining patient engagement in physical rehabilitation for conditions of venous thromboembolism (VTE) prevention is often challenging due to factors such as the repetitive nature of the rehabilitation exercises, and possible insufficient patient motivation. This study investigated the integration of immersive virtual reality (IVR) and gamification to address this challenge. This study explored whether or not integrating the loss and avoidance (LA) gamification dynamic into an IVR rehabilitation game can improve short-term motivation to perform VTE-prevention exercises among middle-aged and older hospital patients. A mixed-design experiment was carried out that involved 28 patients admitted for post-surgical rehabilitation. A smart wearable sensor-based IVR game (SPROUTFIT) was developed, featuring a theme of seed-planting in five stages, where patients perform lower limb exercises to simulate gardening activities. The game employs a level system (“Novice Planter”, “Adept Planter” and, “Master Planter”) to reward performance, with the “loss” component creating a fear of not retaining levels, and the “avoidance” component requiring patients to repeat stages if performance criteria are not met. The patients in the LA-integrated SPROUTFIT (LA-SPROUTFIT) showed significantly higher external regulation compared to the non-LA-integrated SPROUTFIT (NLA-SPROUTFIT) group. LA-SPROUTFIT group also demonstrated significantly higher scores regarding the game experience of competence, flow, and challenge. Game scores were significantly higher in LA-SPROUTFIT group for game stages 2, 4, and 5. Physiological measures indicated that LA-SPROUTFIT resulted in significantly higher heart rate, calorie expenditure, and perceived exertion. Qualitative feedback from interviews revealed that patients generally perceived SPROUTFIT as enjoyable and motivating. However, some patients suggested including various difficulty levels and additional personalization options in future iterations.