Muscles have the ability to adapt to external forces, and when placed under high demand, they generate great strength and power and maintain durability. To accomplish this feat, muscles can change their shape, size, and consistency. You can see these muscular changes in the sculpted physiques of athletes and bodybuilders. As they place greater demand on the muscles, the size and shape of the muscle changes in response to the demand load. And although muscle changes aren't outwardly noticeable in most people, your muscles are constantly altering their size, shape, and consistency in response to your daily activities too. Movement helps muscles maintain their elasticity, and the lack of movement causes muscles to develop some rigidity. From their very smallest component to their largest bulky mass, muscles work in unison to expand and contract. As muscle fibers change their size and shape, they glide over the surrounding fibers. The result is a living woven fabric capable of changing its size, shape, and strength depending on the demands of the moment.