Stretching is more than just a chore taught in elementary school and middle school. Stretching is good muscle maintenance, but the majority of people in western and modern cultures don't know how to stretch or what to stretch.
Stretching is vital to maintain strength, joint health, and mental health.
Strength
Activities that are repetitious in short motions will shorten muscle fibers. Activities that are common in everyday life include working in a seated position, for women carrying a purse on the forearm or hand resting on a purse carried over the shoulder, weight lifting with either free weights or most machines, driving, sitting, and many more. When a muscle is shortened it appears to be weaker than a muscle that is not shortened. For example, if you bend your arm at the elbow and bring your hand to your shoulder then try to lift a heavy object towards your shoulder, it will feel weaker than if you begin with your arm unbent. Bulky muscle, while impressive, is usually more cumbersome and less effective than lean muscle. Often body builders lose function and flexibility and this can cause pain in both the short term and long term. Body builders are often see with their arms hanging away from their sides because the muscles in their shoulders is shortened across the top of the shoulders lifting the arms outward. The same condition is seen when overweight people sit and use arm rests while working on computers, and they too cannot put their arms close into their torso without discomfort.
Joint Health
Our bodies continuously heal and regenerate. When we sustain continuous damage, or excessive damage, we can not heal quickly enough to keep up, and loss of cartilage, wear on bones, and inflammation occur. When we move, the muscles on both sides of the joint engage and bring the bones together so that the friction is increased, and we can bend at the joint with a smooth controlled motion. If the muscles do not relax in between movements or when at rest, the friction does not decrease enough to allow healing, or will cause damage in amounts that our bodies can not keep up with.
Mental Health
Happiness is as much a body movement and posture as it is an emotion. Many studies over several decades have shown that bouncing and hopping improve mood and bring a feeling of happiness. It is nearly impossible to cry while bouncing, and is often employed when carrying babies.
