if the muscle fibers are cyclically exposed to various loads of stress and tension, they become well aligned, take up greater amounts of amino acids and synthesize more proteins. Other physiological benefits to training include an increase in intracellular mitochondria (the powerhouses of the cell), the number of capillaries, total blood flow and total oxygen-consumption capacity, leading to a profound rise in muscle metabolic activity. These increases yield a more well-developed and fatigue-resistant muscle.