## 4 Discussion
They concluded that weights under 400 g should be considered when choosing the implant weight, especially in patients with scoliosis or other spinal curvature affections. In the one-minute standing position, differences between conditions were found only in the LS muscle, mainly in the 220 mL implant, which showed a lower percentage of muscle activation compared to the control and with the 315 mL condition. As expected, muscle activity was higher in the 315 mL condition than in the 220 mL condition, likely due to the increased load requiring more muscle effort to maintain stability. Unexpectedly, no significant differences were found with the 365 mL implant despite its greater volume, and the 220 mL condition showed lower LS activity than the control. These results could be influenced by high variability within the group, as indicated by substantial standard deviations across all conditions, suggesting LS individual differences among the participants that may overshadow the effects of implant volume, a factor that was not explored in this study. Another possibility is a complex muscle adaptation strategy by the LS in response to lower anterior loads. No previous studies have reported such differences, and with our results, we cannot conclusively attribute them to muscle adaptation. These findings emphasize the need for further research to better understand how different implant volumes or external loads affect muscle activity, particularly in the LS. During the reaching phase of FRT, the 315 mL and 365 mL implant conditions showed lower sEMG activity in the LT muscle and higher sEMG activity in the UT muscle when comparing the 315 mL with the control condition. These muscles did not show a linear trend across implant conditions but only a variability of muscle activity between conditions, also with a high standard deviation. Overall, the added implants did not demonstrate a clear negative trend toward muscle imbalance compared to the control condition, as expected for functional, active, and healthy individuals. These results suggest that most participants counterbalanced for the additional weight with increased LT muscle activity for scapular stability accompanied by decreased UT muscle sEMG activity, but only in the 315 mL implant condition, representing reduced UT muscle overload. During the return phase, the percentage mean activities of the LT and UT decreased compared to the reaching phase for all conditions, as expected. Although the results across implants also showed a comparable pattern to those observed in the reaching phase, only one condition comparison was statistically significant, with the UT muscle showing a decreased percentage of sEMG muscle activity when comparing the 220 mL condition to the control. A related research study by [PERSON] and [PERSON] (2022) looked at electromyographic changes in the thoracic and lumbar erector muscles as well as in the UT muscle [21]. They found that, when silicone gel implants were used to increase volume by six times in people with 200-250 mL mammary volumes, achieving volumes of 1200-1500 mL, UT sEMG activity increased during the sit-to-stand activity, a different activity that does not require the same muscle activation patterns than those in this study. This significant absolute increase in volume was beyond what the participants in the present study achieved with the 365 mL implant, which also can explain the differing results. In addition, the present study involved a group of young female volunteers who were mostly very active, which was not assessed in the study by [PERSON] and [PERSON] (2022) [21]. This could influence the results relative to UT and LT sEMG activity for potentially greater postural control capabilities. Ultimately, an evaluation of the muscle activation timing would have provided a better insight into the dynamics of muscle coordination during FRT. Future studies should consider this evaluation to better understand the dynamic interactions between these muscles.