Yes, but that doesn't mean lying still like sit-ups. Or pedal, just lie on the floor and pretend to pedal an imaginary bike. The correct action is to press the floor with your back down and put your hands behind your head. Lift the knee at a 45-degree angle, and use the pedal. The left ankle should touch the right knee, and then touch the left knee with the right ankle. Cross your legs vertically, lie face up on the ground, cross your legs on the ground, and put your head in your hands. Raise your legs until they are perpendicular to the ground, and then raise your head. Stop at the highest point and breathe once, then repeat. The abdominal lifting movement of lying and lifting legs also makes full use of the strength of abdominal muscles, with the focus on the following strength. Exercise: Lie on your back with your hands at your sides and your feet crossed. Abdominal muscles lift legs hard and knees bend. Then put it down. Say it again. Because the action is relatively simple, we must rely on the strength of the abdomen rather than the strength of the thigh.