What determines muscle strength?

Muscle strength depends on the number of muscle fibers that make up the muscle, the length of the muscle itself, the mass of contractile proteins and their contractile ability, the frequency of nerve impulses that go to the muscle. With physical exertion, muscle mass increases, so nerve impulses cause greater contraction. Also, when muscles work, blood flow increases and gas exchange occurs better. In the absence of work, the muscles decrease in size, become flabby, lose turgor and atrophy.