Abdominal contraction requires abdominal muscle contraction, and the lumbar spine is always close to the ground, and it must not be lifted, let alone the waist to complete the action.

Just lift the shoulder blades and tighten the abdominal muscles. It is impossible to lift your body. Then your abdominal muscles don't have the strength to press the lumbar spine at all.

Then do this, the calf is placed on the stool, and the knee joint is 90 degrees, which is convenient for pressing the lumbar spine. Be careful not to pull your head by hand, which will easily damage the cervical spine.

Leg lifting requires that the lumbar spine must be pressed down and close to the ground. However, leg lifting is more difficult than belly rolling. Adjust the difficulty of exercise by straightening or bending your legs and raising your height. Remember that the lumbar spine must not be suspended.

If the above movements are difficult to control, just do static movements and keep them for a certain period of time, and you can achieve the same exercise effect and adjust the angle to a position that you can absolutely master.

If the waist is sore, it means that the posture is wrong, the waist is full of strength, or the abdominal muscles are insufficient, and you need to stop resting immediately.