The key to practicing abdominal muscles is the intensity of movements, not the more times, the better. For example, if you can do 200 sit-ups at a time, you might as well do 10 from both ends. Because being able to do more than 200 exercises is endurance, the thickening of muscle fibers is not obvious.
Four actions to exercise abdominal muscles: sit-ups, supine leg lifts, double-headed leg lifts and suspended leg lifts (the intensity increases in turn). If you can do 10 to 20 sit-ups, do sit-ups and leg lifts; If you can do 10 to 20 supine leg lifts, you can do both ends. And so on. Practice three times a week, and practice about three groups in one movement at a time.
In addition, fat with a body fat rate higher than 10% will cover abdominal muscles. This is why sumo has no muscles. If you have a small belly, you need to jog for about 40 minutes to lose fat. About 3 to 5 times a week. If you can't run for 40 minutes at a time, you can walk for a while.