Stretching before a workout helps your body to become more pliable, which decreases your risk for injury. You want to stretch the main muscle groups that you plan on working during that exercise session. For example, if you’re going to be running, or doing lower body strength exercises, you probably want to stretch your hamstrings, quads, glutes, and calves.
Stretching keeps the muscles flexible, strong, and healthy, and we need that flexibility to maintain a range of motion in the joints. Without it, the muscles shorten and become tight. Then, when you call on the muscles for activity, they are weak and unable to extend all the way. That puts you at risk for joint pain, strains, and muscle damage.
For example, sitting in a chair all day results in tight hamstrings in the back of the thigh. That can make it harder to extend your leg or straighten your knee all the way, which inhibits walking. Likewise, when tight muscles are suddenly called on for a strenuous activity that stretches them, such as playing tennis, they may become damaged from suddenly being stretched. Injured muscles may not be strong enough to support the joints, which can lead to joint injury.
Regular stretching keeps muscles long, lean, and flexible, and this means that exertion "won't put too much force on the muscle itself," says Nolan. Healthy muscles also help a person with balance problems to avoid falls.
