Because these muscles are the muscles that have a low fatigue rate, they can be used to basically support our body to give it posture. Now, these are the muscles that are used in middle distance events. For example, if we're running, let's say 400 or 800 meters, these are the muscles that we're going to use. These are the muscles that are used when we basically need to exert a very large force. For example, when we're lifting a very heavy weight. And that only requires several seconds.