For boys, it is difficult for them to do some difficult movements, because their skeletal tissues are fully developed and the gaps between bones are very small. If they do some difficult movements, their bones will be damaged, which will cause serious damage. In addition, the boy's skin is tight, there is no excess fat, and he looks very backbone. Look at this boy, he is thin and has no meat.
Let's talk about girls. Girls are born with well-developed bones, and there are a lot of gaps between bones. Plus, they will have an advantage over boys, so they are more likely to do some difficult movements. That's because girls have good physical flexibility, which boys can't compare with. In addition, girls will have a lot of meat, which will make them look soft and have an impulse to pinch them.
Girls are weaker than boys in many other aspects, which may be due to their own genetic problems or acquired development. Anyway, these are all possible, and we need to continue to study which is the most correct answer. Because all this is not necessarily the best answer, we need some relevant information and data to analyze this point.