Does the number of muscle fibers change throughout life?

In humans, the number of muscle fibers always changes. All healthy people have muscle. During the development of the body, muscle fibers become many times larger, as a person grows. But even after a person has stopped growing, the number of muscle fibers changes. Their number can either increase when a person is engaged in sports or physical labor, or decrease. It is due to the fact that the muscles are straining that their number increases. But with prolonged load, the opposite process can also begin.