Does the amplitude of the muscle response increase because t

Does the amplitude of the muscle response increase because the response of each muscle fiber increases or the number of muscle fibers responding increases?

Solution

the alteration in muscle response amplitude depends on the stimulus

when there is no stimulus muscle response is neutral

when there is minimal stimulus muscle response amplitude increases by the contraction or relaxation of the muscle fiber

when there is more stimulus the muscle response amplitude is increased as more motor units are recruited at site and these muscle fibres start contracting or relax in response.

however when the threshold is reached further increment in the stimulus will not affect the muscle response amplitude.