In martial arts novels, people who describe deep internal forces often say that "the temple rises." Why?

Describe the internal force of people can be bred almost anywhere.

Because the weakest place outside a person is the temple, you can't hit it here. Many martial arts novels breed people's true spirit (that is, internal strength) in different places to resist external shocks. For example, if you practice Qigong regularly, you can break the stick by gathering qi in the abdomen. Similarly, if a person can practice his internal skills so deeply that even his temples are full of qi, then he must be very powerful.

Martial arts novels have exaggerated elements, but I also like martial arts!