Depression on both sides of buttocks is often a natural form formed by no or a small amount of fat accumulation on both sides of buttocks. It has nothing to do with whether the gluteus medius is developed or not. Usually, men are more likely to form this appearance because their natural posture is to put their pelvis on the frustum of a cone. From the aesthetic point of view, men's posture will be more bodybuilding than women's, reflecting their inverted triangle posture. However, women's lack of this piece of fat will make the gluteal line of S curve missing. Therefore, this area is theoretically formed by fat, and the more developed gluteal muscles are, the easier it is to lose.

The gluteus medius is an endurance posture-stabilizing muscle, just like the abdominal muscles. Even if the training is developed, the girth will not be much.

1. Tightening the gluteus maximus will inevitably lead to depression in the figure, just as tightening the pectoralis major will lead to depression on the lateral edge of the middle chest.

These are the inevitable results of the bone structure of the body and the direction of muscle fibers. The depression of bodybuilders after tightening their chests is mainly the inevitable result of muscle fiber direction. Not only can it not be filled, but the more developed the pectoralis major, the more obvious the depression. The fan-shaped structure of pectoralis major and the direction of muscle fibers cause the depression on it. Hip is the visual effect of the contrast between the greater trochanter of femur and the surrounding tightening muscles after gluteus maximus tightening. 1. I don't agree with other answers. Too little fat. I think it is more likely that some girls have too much fat, and there are more deposits in the lateral abdomen and the upper part of the lateral buttocks, which has caused visual impact. This should be analyzed in detail according to the situation of the subject. What is the whole body fat? Is there a serious problem with posture or movement, resulting in excessive local fat? This is a big problem.

2. I have also seen a part of the buttocks sunken, the body fat is ok, the muscles are ok, and a piece is missing out of thin air. This is probably caused by congenital or trauma, and this situation is basically insoluble.