A quick fix for abdominal muscles: Lift your legs to write:
Lie on your back, straighten your legs, lift them together, straighten your toes, and write in the air.
When exercising, keep your neck and arms close to the mattress and lift your buttocks.
The benefit of this method is that it can exercise the rectus abdominis and the muscles on the side of the abdomen.
You can start with the simplest characters such as "one, two, three", and then practice characters with four borders and large movements of the legs, such as "national map". Each time, you only need to practice to the abdomen. Creatine swelling is enough.
