Fast fatigable motor unit recruited

Motor UnitEach single motor neuron and the muscle fibers it innervates constitute a motor unit.Each spinal motor neuron innervates only one kind of muscle fiber so that all the muscle fibers in a motor unit are of the same type.On the basis of the type of muscle fibers they innervate, and thus on the basis of the duration of their twitch contraction, motor units are divided into S (slow), FR (fast, resistant to fatigue), and FF (fast fatigable) units.(Refer: Table 17)(Refer: Ganong&;s Review of Medical physiology 24th edition, pg no: 108-109)