Sit-ups, a form of exercise. Lie on your back, put your legs together, raise your hand, contract your abdominal muscles, swing your arms forward, and quickly become a sitting position. Keep your upper body bent forward, touch your feet with your hands and bow your head. Then return to the sitting position. So continuous. Practice sit-ups, the speed varies from person to person. You can try to do it five times a minute at first, and then slowly increase it until it reaches about 30 times. Many women under the age of 30 practice for the purpose of preventing gynecological diseases. At this time, it is best to control the frequency at 45-50 beats per minute, and gradually decrease with the increase of age. It is enough for people over 50 to do 25 beats per minute. For people who have a certain fitness foundation, they want to strengthen their abdominal strength through practice and ensure that they do it about 60 times a minute.