First, the internal force promotion is like a curve. First of all, I think the internal force promotion is like a curve. It has a rapid rising period and a gentle rising period. The rapid rise is the fastest when people practice strong martial arts when they are young, but there will be a gentle rise period when the internal force is deep. The storage position of internal force written in the novel is generally at the two acupoints of Dantian and Zhongshan. Of course, others will store the internal force in other places. Since there is a storage place, there must be an upper limit, but few people can reach it.
Second, the deeper the promotion, the more difficult it is. In Jin Yong's novels, we often see such a thing that some young people practice faster. Of course, the role of the protagonist's aura is not ruled out, but in their cultivation process, they often surpass some older roles. Of course, the internal strength of the older generation will get deeper and deeper with age, but their internal strength cultivation speed is not very fast, but it seems to have encountered a bottleneck. Therefore, it can be considered that the deeper the internal strength, the more difficult it is to improve, and the higher the requirements for talents will be.
Third, the age limit is obvious to many people in literary works, including first-class masters, second-rate masters, third-rate masters and so on. Some people in the older generation have deep internal forces, but for young people, they are sometimes unable to compete. This is because although they have deep internal forces when they are old, they will definitely feel overwhelmed with age, leading to a gradual loss. After all, the human body will age slowly with time, but the place where internal force is stored will not be as big as when it was young, so I think there is an upper limit to internal force, but the upper limit of each person is different.