Sit-ups: lie flat on the ground, put your calves on the bench, then shrink your shoulders and create an arc in your abdomen, as if to roll forward. Don't stretch your head so far that it touches your legs, because it means that your back will leave the ground, so your hips will begin to share the work that should be done by your abdomen. When descending, let your shoulders slowly return to the ground and never relax your abdominal muscles.
Vertical leg lift: to do this action, first of all, pay attention to avoid swinging, tighten your body and control the speed of action. In order to stimulate the intercostal muscles, the knees turn left and right, which also exercises the abdominal oblique muscles. The key to correct leg lifting is to stretch your hips forward. If you just lift your legs, of course, it is very comfortable, but it only stimulates the buttocks rather than the abdominal muscles. This method is difficult to practice, but it will completely stimulate your abdomen. The movement speed varies from person to person, but it is necessary to ensure that the leg release process is slow and prevent swinging.
Sit and lift your legs: This action can better stimulate the lower part of abdominal muscles. Sit on the edge of the bench, stretch your legs forward, lean back about 10 degrees, grasp the edge of the bench and keep your body balanced. Don't bend your knees, lift your legs up until your toes are parallel to your eyes, and then slowly lower them. Control and tension are very important in the whole movement, and a slight negligence may lead to lower back injury. As the abdominal muscles become more and more tired, you can gradually bend your knees until you understand them thoroughly.