## 4 Discussion  
The present study hypothesized that the addition of IVR to a high-intensity aerobic exercise program carried out by patients with PD on a smart cycloergometer could result in better therapeutic results than those obtained through just the use of a cycloergometer on its own. This hypothesis arose from the studies carried out by [PERSON] et al. [55] and [PERSON] et al. [56], which indicated that when people obtain pleasure from an exercise session, they are more likely to adhere to it long term, and thus identifying ways to manipulate the exercise experience to induce a \"pleasure\" response in people who do not exercise regularly is an important scientific challenge for overcoming levels of physical inactivity. Exergames (ganification of exercise) may be associated with greater interest, greater pleasure, and greater enjoyment than traditional physical activity. Since exercise becomes part of a virtual experience [57], effort is attenuated perceived, which maximizes the enjoyment of exercise while increasing motivation during training [58; 59; 60]. Previous studies carried out in a healthy young population [61; 62; 63] showed that training with IVR in contrast to the same method but without IVR generates a higher heart rate (188 bpm; 12.9 METs per session), while the perception of effort is lower. [PERSON] et al. [62] indicated that the use of exergames causes intense myoelectric activity along with resistance training, which does not occur during traditional resistance training. On the other hand, [PERSON] et al. [63] developed resistance training with IVR and traditionally with the same volume, observing much more favorable adaptations in the IVR group in terms of body composition, cardiometabolic parameters, and muscular endurance strength. The data collected seem to confirm this hypothesis, as this high-intensity exercise program using a cycloergometer with the additional support of IVR HMDs produced significant improvements in dynamic balance and gait when these were measured with the TUG test, the TUG dual-task test, and the Tinetti scale, suggesting a decreased risk of falls, an important issue in patients with  
Figure 3: Pre- and post-intervention scores of MDS-UPDRS (parts I, II, III, and IV). PD. Additionally, a significant improvement was observed in PD symptomatology when measured with the MDS-UPDRS, as well as the patients' quality of life when measured with the PDQ-39 scale. Finally, it should be noted that, although not significant, an improvement was also observed in lower limb strength as measured with the FTSST, while in the CG, there was a slight deterioration. These data are in line with previous research on the therapeutic benefits of high-intensity aerobic exercise in PD patients [11; 64; 65]. Although there are no previous studies combining a smart cycloergometer and IVR to carry out high-intensity aerobic exercise in patients with PD, there are also some studies that explored the use of forced pedaling with IVR [66] or the use of active video games in populations of healthy young adults [67] and how exposure to virtual and immersive scenarios influences the subject's perception of effort. According to [PERSON] et al. [66], virtual scenarios can reduce the perception of effort, and according to [PERSON] et al. [67], the type of activity performed can have the same effect. Our study confirms this fact, as the group that did the pedaling work with IVR presented lower RPE values while having traveled a greater distance (1400 m) than the group that exercised without IVR. On the other hand, while there are no previous studies like ours proposed for patients with PD, there is research where this type of high-intensity forced cycling work has been performed without the use of the IVR component, which also generated significant improvements across the variables considered in our study. In relation to improvements in balance, [PERSON] et al.