[Supine leg raise] mainly exercises the lower abdomen. Lie flat on the ground, put your hands flat on both sides of your body to stabilize your body, and bring your feet together and bend your knees to approximately 90 degrees. During exercise, lift your buttocks hard with your lower abdomen, bring your knees as close to your chest as possible, and then slowly return to the starting point. Combine it with the meager "straight leg raise" movement in the next article to create a first-level compound movement. Repeat each of the two actions 15 to 20 times. Tip: Slightly retract your jaw to make the movement more difficult.