1 Lie on the ground with your abdomen twisted, with your legs together, your body straight forward, your elbows bent, and your hands on the back of your head. Then bend your right leg properly with your knees, and bend your left leg upward with your knees so that your calves, thighs and thighs are perpendicular to the ground respectively. While lifting the leg, lift the right upper body to the left front, so that the right shoulder is off the ground, the right elbow is as close to the left knee as possible, and the abdomen is compressed. Do it again after changing sides.

Sit-ups, knees together, lying flat on the ground, waist and back fully stretched on the ground, elbows bent with both arms, head supported with both hands, shoulder blades tilted backwards, so that arms can lean on the ground as far as possible. Exhale at the same time, abdominal force, lift the upper body. When lifting, the chin is retracted, the arm swings forward slightly, so that the elbow touches the knee and the feet keep on the ground. Then lie down slowly, regain your posture and do it back and forth several times.

3 Shoulder lifting is also a preparation posture for sit-ups. The legs are bent together, and the legs are about 90 degrees. Put your hands on your head, lift the parts above your back while exhaling, lift your shoulders off the ground, and close your chin, but don't lift your upper body too much, let alone do it. Try to keep your back down, including your lower back and hips, and keep your feet off the ground. Use the muscles of your upper abdomen to complete the lifting action.

4 Lift your knees and lie flat on the ground, put your legs together, bend your left arm, hold the back of your head with your left hand, stretch out your right arm, stretch your right hand forward to press your abdomen, pull up your right shoulder and lift it off the ground, and touch the outside of your left knee with your right hand. Your arm is straight and your right abdomen is particularly compressed, which can strengthen the muscle strength of the oblique muscles inside and outside your abdomen.