When we stretch, we keep the muscles flexible, strong, and healthy, and we need that flexibility to maintain a range of motion in our joints. Otherwise, the muscles shorten and become tight. Consequently, the muscles cannot extend all the way when you call on them. You could suffer from joint pain, sprains, and muscle damage. During rehabilitation, stretching is often recommended. The purpose of stretching is to increase muscle length and range of motion, or to align collagen fibers during muscle recovery.