(1) Exercise abdominal muscles, whether it is supine abdomen (upper abdomen) or leg lifting (lower abdomen), the movement must be slow, and always maintain "confrontation" from muscle elongation to contraction peak. Never use inertia to make it stronger, and the lumbar spine is easy to be injured. By the way, sit-ups are easy to hurt the hip joint because of their large amplitude, so the coach doesn't recommend them at present, so they are changed to abdominal rolling with smaller amplitude and more isolated motion parts. As @ Xu Chen said, it is easy to hurt the cervical spine by holding your head and doing sit-ups, which is a wrong action.

2) In order to make the shape look good, it is very important to fully stretch after exercise. Many people will have abdominal pain after practicing for a few days, but this is lactic acid accumulation, which does not mean that the practice is in place. Stretching will relieve the pain.

(3) Abdominal muscles and psoas muscles are "two sides of the same coin". While exercising abdominal muscles, we should also pay attention to the exercise of lumbar muscles. Otherwise, the strength of abdominal muscles is increasing, and it is unbalanced before and after, and it is easy to strain the waist during exercise.

(4) As a small muscle group, abdominal muscles are actually easier to practice. In a few months, there will be obvious changes. It is difficult to consume abdominal fat. Many people can't develop abdominal muscles for a long time, but the problem is not to gain muscle but to lose fat. It is necessary to reduce oil intake and increase aerobic exercise.