Even the chest muscles are divided into three parts, upper, middle and lower, not to mention the abdominal muscles. Judging from your abdominal muscles, you practice upper middle school. What equipment do you usually do? If you want to practice under the navel, that is, the lower abdomen, I suggest you practice sit-ups, feet up, head down, the more oblique the better. Bend your legs a little, touch your knees every time you practice and measure yourself. For example, I practice five groups in a group of 50. Practice 50 at a time, take a break and continue 50. I felt very tired at first, but I felt relaxed after practicing late. You can "add more". "Overweight" means that when you are practicing, you are holding a barbell plate in your hand, starting with 10KG. Similarly, your head should touch your knees, and your body and chair should be at a 90-degree angle.

I hope it will help you and be adopted. Thank you.