## 4 Discussion  
This single-arm exploratory study investigated the immediate effects of a 6-week iVRE program on PI and PPTs, as well as the influence of a single bout of iVRE on PPTs in a sample of 11 patients with FM. Key findings include: (i) Improvements in PI by the end of the program, which were clinically and statistically significant in this sample; (ii) no observable changes in PPTs following either a single session or the 6-week intervention, implying that, in this sample, there would be no changes in MPS, nor would the exercise-induced hypoalgesia mechanism be activated; (iii) 81.81% of participants transitioned to a lower-risk category on the KSMT after the intervention; (iv) 63.63% of participants were classified as good responders to iVRE in terms of PI reduction; (v) medium-risk patients demonstrated greater absolute and proportional reductions in the NRS compared to high-risk patients; (vi) feasibility parameters showed an enrollment rate of 1.44 patients per week, a recruitment rate of 76.92%, and a retention rate of 55%; (vii) the proportion of women in the sample was 90.9%, which aligns with the epidemiological profile of FM, which predominantly affects females; and (viii) the intervention was safe, with no adverse events reported and no protocol modifications required. In the present study, we used a head-mounted device that provides a high level of immersion, allowing exercises to be performed in a sensory-enriched virtual environment, similar to that used in a previous study conducted with patients with FM [31]. While these characteristics support the application of iVRE, it is important to consider potential adverse effects, such as nausea, motion sickness, headaches, and discomfort associated with head-mounted devices [29]. In our study, no adverse effects were reported during the application or after the iVRE protocol, which could be attributed to the duration of the intervention, the characteristics of the FitXR game, and the small sample size. Recent literature reviews [26, 27] show that only two studies have previously used immersive VR-based interventions in individuals with FM, one of which combined it with cognitive-behavioral therapy (CBT), reporting very high satisfaction in 84% of cases and 96% of patients experiencing minimal or no adverse effects [44]. The other study, like our exploratory study, applied iVRE in FM but did not explicitly report the presence or absence of adverse effects [31]. Additionally, two previous studies on individuals with FM applied non-immersive VR for durations similar to those in our study: one associated with physical exercise [52] and the other with CBT [53], both reporting very high satisfaction and absence of adverse effects. Considering these results and those from the present preliminary study, there are indications that short-duration iVRE interventions may be well tolerated by patients with FM in the short term, which is consistent with previous recommendations [48]. Future controlled studies with larger samples should confirm these preliminary findings. Although interventions involving iVRE in patients with chronic musculoskeletal conditions remain incipient [29], the incorporation of virtual reality-based physical exercise in rehabilitation processes is gaining attention due to its potential benefits on several \begin{table}
\begin{tabular}{c c c c} \hline  & **Total** & **High Risk Pre** & **Medium Risk Pre** \\ \hline N (\%) & 11 & 8 (72.73) & 3 (27.27) \\ Responders; n (\%) & 7 (63.63) & 4 (50) & 3 (100) \\ Non responders; n (\%) & 4 (36.37) & 4 (50) & 0 (0) \\ NRS pre; mean (SD) & 7.36 (2.01) & 8.25 (1.28) & 5 (1.73) \\ NRS post; mean (SD) & 5 (2.76) & 6.25 (2.05) & 1.67 (0.58) \\ Reduction in NRS; mean (SD) & 2.36 (2.66) & 2 (3.02) & 3.33 (1.15) \\ \% Reduction in NRS; mean (SD) & 33.13 (36.33) & 20.56 (34.97) & 66.67 (0) \\ \hline \end{tabular} Abbreviations: NRS: Numeric rating scale, SD: Standard deviation.  
\end{table} 
Table 3: NRS score changes post-iVRE intervention by risk stratification levels.