Answer:
motor units
Step-by-step explanation:
Type I motor units are small, smooth, slow motor nerves, while Type II motor units are innervated by large, fast motor nerves. Today, instead of slight differences in motor neurons, there is a continuous input for activation. This allows a systematic mobilization of the motor units to accommodate a specific tension, speed and metabolic requirements of muscle contraction. Typically, the Type I motor unit is recruited during low intensity exercise.
When more effort is activated, Type II motor units are required and incremented. When low intensity activity is prolonged, Type I motor units are initially recruited.