There is a saying that makes sense. Abdominal muscles are not made, they are thin. The so-called vest line is the dividing line between rectus abdominis and external oblique muscle.

So it is not clear whether to use abdominal muscles or vest line to determine this person's fitness level. The only certainty is that this person must be very thin.

When the male body fat rate reaches about 12% and the female body fat rate reaches about 20%, there will be obvious abdominal muscle contours, even if you don't exercise.

Compared with other muscles in the body, the abdominal muscles are very small, and even after long-term fitness, the increase is very limited, especially for women, because testosterone, the main muscle growth hormone in the body, is insufficient, only 1% for men. It is more difficult to gain muscle than men, and it is more difficult to grow abdominal muscles.

To judge a person's fitness level, we should look at the whole, not just the abdomen. The author also found that many friends only practice abdominal muscles crazily, ignoring the training of other parts, so the "figure" trained can't be good.

The author thinks that the direction of female fitness should be the combination of anaerobic exercise and aerobic exercise. Anaerobic exercise can focus on exercising hips and legs, which is very important to show female charm. Aerobic exercise is a necessary means to keep the body fat rate low.