## 4 Discussion
### Muscle Damage and Stress Markers  
Since an increase in abdominal load due to fetal development causes pelvic pain, muscle stiffness, and a vicious cycle of body imbalance, inflammation and muscle damage are caused, and various methods have been used to reduce inflammation and muscle damage [56; 57]. In particular, Pilates exercise is used as rehabilitation to treat or prevent inflammation and muscle damage by repeating muscle contraction and relaxation [56]. However, rather than the general public, the subjects who participated in this study were all pregnant women, and accurate information on the intensity of Pilates exercise is not yet known. Therefore, although in this study the activity of muscles related to body water balance and pelvic stabilization was shown by setting the intensity of Pilates exercise based on ACOG guidelines, the Pilates exercise program and intensity may prevent muscle damage and increased stress due to excessive and repetitive movements. Therefore, the muscle damage index and the stress index confirmed the Pilates efficiency applied in this study. CK is a biochemical indicator of muscle damage that is present in muscle in large quantities and has a high correlation with the type of exercise and intensity, time, and quantity [32; 33]. Furthermore, LDH, a representative muscle damage marker, is a result of muscle damage due to excessive exercise. It is known to increase with exercise intensity [58; 59; 60]. Interestingly, in the results of this study, CK and LDH between the periods within the group showed a tendency to increase significantly after the period compared to before (CK: \(z=-1.700\), \(p=0.089\), \(r=0.425\); LDH: \(z=-2.603\), \(p=0.009\), \(r=0.651\)). AST, another indicator of muscle damage, is generally used as an indicator of liver damage, but is known to increase after muscle injury according to some studies [59; 60]. As a result of confirming the difference in the amount of AST change in this study, similar to LDH, it was found to be significantly reduced in the PE group compared to in the CON group (Table 4), and in the difference between the periods within the group, only the CON group was significant compared with the before and after. It showed a tendency to increase. Previous studies have shown that these results may differ depending on the type of exercise, the degree of muscle contraction, and physical overload in the muscle damage of the human body [60], whereas these results show that the muscle damage that occurs during pregnancy is partially reduced by Pilates. It is believed that the Pilates program conducted in this study improved muscle strength within the range that did not cause muscle damage. Changes in body shape during pregnancy and pain such as low back pain induce stress in the tissues of cells, increasing the level of stress hormones along with inflammation [61]. In this study, as a result of confirming the difference in the amount of change in CRP, which is an inflammatory indicator that increases due to non-specific stress in the human body, there was no significant difference between the two groups. The CON group showed an increasing tendency, but there was no significant difference (Table 4). In addition, the stress hormone cortisol also increased significantly after in both groups compared to before (CON group: \(z=-2.201\), \(p=0.028\); PE group: \(z=-2.547\), \(p=0.011\); Figure 2); there was no significant difference in the amount of change between the two groups. This is believed to be due to the inevitable physiological changes that occur during pregnancy, and since there are various factors that cause inflammation and stress, further research is necessary. Furthermore, the small number of subjects who participated in this study seem to be insufficient to generalize the results. Recently, the fertility rate in South Korea has continued to decline, and there has been great difficulty in securing subjects to participate in studies.