As autolysis takes place, muscles loosen again. If a limb moves a lot, the muscle fibers can shorten a great deal and become more inefficient. In other words, the muscle can only shorten as much as the tendon stretches. This would happen if you were trying to lift a 1000 pound table top. Since sarcomeres are arranged in series, each adds to the shortening of the whole muscle.
Stronger muscles have many cells arranged in parallel like the jaw muscle.
Fast, but less powerful muscles, like the triceps, are composed of fewer longer fibers. Treppe is the response of a muscle to a frequency of stimulation that results in a partial relaxation between contractions. Tetanus is the response of a muscle that is stimulated so frequently that it has no time to relax between stimulations. There is only enough present in a cell to last a few seconds. In mammals, creatine phosphate is in equilibrium with ATP with the equilibrium concentration far toward ATP or, in other words, when there is a great deal of ATP and very little ADP, some of the phosphate will be transferred to creatine to make creatine phosphate.