Muscles in the human body are made of a mixture of different muscle fiber types
Muscles in the human body are made of a mixture of different muscle fiber types. The composition of these muscles varies depending on the activities they are used for. Postural muscles for instance (e.g. calves and spinal muscles) are mainly made up of slow twitch fibers as they do not need to generate much power and are considerably resistant to fatigue. Furthermore, during muscle contraction, only the required fibers will contract. Only slow-twitch fibers will contract if there is a weak contraction. Fast oxidative and fast glycolytic fibers will contract if powerful effort is made (heavyweight lift) along with the slow-twitch fibers, with the former fibers contracting last.