Purpose : The aim of this study is to determine changes to the thickness of core muscles, e.g., transversus abdominis (TrA), external oblique (EO), and internal oblique (IO), after plank and Kegel exercises and to compare the effects of the two exercise methods. Method : The study divided men and women in their 20s into two groups, Kegel and plank, by randomly allocating 30 males and 30 females to the targeted groups. To achieve the purpose of this study, we examined the thickness of core muscles after the participants performed plank or Kegel exercises. Results : 1. In the Kegel group, abdominal muscle thickness increased with time, and there was a statistically significant difference in the thickness of the TrA. 2. In the plank group, abdominal muscle thickness increased with time, and there was a statistically significant difference in the thickness of the TrA. 3. After the experiment, muscle thickness of the abdominal muscles in the plank exercise group were higher, but there was no significant difference between the Kegel exercise group and the plank exercise group. Conclusion : Both plank and Kegel exercises are recommended for core muscle stabilization, and based on the results of this study, Kegel exercise is either used as a core stabilizing exercise or as a plank exercise for the weaker patients or women.