## 4 Discussion
Research suggests that H\({}_{2}\)O\({}_{2}\) influences muscle cell differentiation. While the biochemical mechanisms are not yet fully understood, it is believed to occur through mitochondrial stimulation [57]. In this study, a concentration of 700 uM H\({}_{2}\)O\({}_{2}\) reduced cell viability by about 30%. Thus, despite not observing a significant reduction in viability, this concentration changed the cell's bioenergetics, causing increased ROS levels, intensified availability of NO, hyperactivity of COX, and leaning toward mitochondrial depolarization. [PERSON] et al. [58] demonstrated that when exposed to H\({}_{2}\)O\({}_{2}\), myoblasts show an increase in the number of apoptotic cells, corroborating our findings. There is evidence suggesting that PBMT decreases apoptosis induced by myotoxic agents, increases the anti-apoptotic protein BCL-2, reduces the pro-apoptotic protein BAX, and decreases the activity of CASP 3 and CASP 8 [58; 59; 60]. In this study, late apoptosis at the doses of 9 J and 60 J was not altered compared to the control; however, both doses increased the number of cells undergoing early apoptosis. There was a reduction in late apoptosis in cells exposed to H2O2 and irradiated with 9 J and 60 J doses. Conversely, both doses enhanced the presence of early apoptotic cells. Extrinsic and intrinsic signaling pathways regulate apoptosis and can be mediated by ROS, which, at high levels, can activate this process by negatively regulating pro-survival proteins and through mitochondrial pathways, such as the release of cytochrome c, which feeds back into ROS production [53]. This condition could partly explain the observed results. Therefore, it is possible to infer that PBMT-sMF, when used in isolation and at low doses, does not alter redox homeostasis; thus, the generation of reactive species may be insufficient to induce apoptosis. Complementing the evaluations of cell death mechanisms, no significant differences were observed in the number of necrotic cells in the PBMT-sMF group, nor the cells irradiated and exposed to H2O2. [PERSON] et al. [15], using a continuous-wave laser device (808 nm), found no differences compared to the control, corroborating our results. Nonetheless, they observed an increase in necrosis after 24 h in the group exposed to stress from nutritional deficiency and treated with the laser, compared to the group of stressed cells that were not irradiated. The authors attributed their results to the production of ROS immediately after exposure, which eliminates non-viable cells, and subsequently (48 or 72 h post-exposure) acts beneficially on the viable cells. Future studies are necessary to better understand the reduction in necrotic cells observed in the co-treatment (PBMT-sMF + H2O2). The primary findings of the present study are summarized in Table 3. Collectively, the data indicate that the positive responses elicited by PBMT-sMF are intricately linked to the activity of COX, exhibiting a dose-dependent relationship that is further modulated by the cellular state (oxidative vs. non-oxidative). These results underscore the importance of understanding the specific contexts in which PBMT-sMF exerts its effects. To deepen our comprehension of these mechanisms, further research is essential. Future studies should explore the intrinsic responses and cellular signaling pathways activated by PBMT-sMF over extended time intervals post-irradiation (24, 48, and 72 h). Additionally, investigating the optimal timing and response window, along with the effects on myogenesis, can provide critical insights into the therapeutic potential of PBMT-sMF in muscle regeneration and repair processes. This study has its limitations. Firstly, it evaluated only immediate responses following a single exposure. Secondly, it assessed PBMT-sMF as a combined technique, which precluded the possibility of separately analyzing the effects of photobiomodulation and  
static magnetic fields and the impact of subsequent exposures.