The Ability to Develop Increasing Levels of Force in an Intact

The ability to develop increasing levels of force in an intact muscle composed of both fast- and slow-twitch muscle fibers typically involves:

A) Recruitment of slow-twitch muscle fibers before fast-twitch muscle fibers.
B) Tetany of fast-twitch muscle fibers at lower stimulus frequencies than those for tetany of slow-twitch muscle fibers.
C) A progressive recruitment of more muscle fibers within a given motor unit.
D) A progressive increase in the amplitude of the intracellular Ca⁺⁺ transient.
E) A progressive decrease in the threshold for an action potential in the skeletal muscle.