Influenced by a certain gene, they discover that there are mice that run 25% more than normal. This gene seems to increase the production of a certain muscle fiber, that of type IIX, or rather, that almost all other fibers become this type of fibers. Experts are surprised by the influence of this muscle fiber. In fact, this type of fibers is not well known, and they did not believe that it had such a close relationship with its duration.