Muscles work by contracting. All muscles cross over at least one joint, (sometimes two) and the action of contracting a muscle causes that joint to move. A good example is the quadricep (thigh) muscle. It originates from the front of your hip (the anterior superior iliac spine), crosses over your knee joint, and inserts (as a tendon), to your shin bone (tibia). The action of contracting your quadricep muscle moves your lower leg forward, as it straightens your knee.
Muscles are the motors of your body. All of their action is due to their contraction. They can do more work if they have greater contractile strength. Contractile strength is greater when the muscles are longer. The longer the muscle, the more work it can do when acting on a joint. Stretched muscles are longer muscles.
Stretching allows greater extension of a joint when moving. For example, if you are a runner and stretch prior to running, your stride will be longer. If the stride remains the same length, then the muscles involved will be doing less work.
Stretching helps prevent injuries. The more flexible a person is, the less the likelihood of a torn or strained muscle. Over time, proper stretching strengthens both ligaments and tendons. Ligaments attach bone to bone, tendons attach muscles to bone.
Stretching promotes faster recovery, since stretching the muscles helps to move toxins and waste products of muscular exertion out of the muscles and into the bloodstream, where they can be broken down and eliminated. Stretching relaxes your body. Relaxing your body allows you to experience less intense negative emotional states.
Muscles that are tight waste energy. Stretching allows you to become aware of areas in your body that are held with undue tension, so you can release them.
Stretching feels GOOD!!! Anyone, at any age, can stretch. It does not matter where your flexibility level is when you begin, as long as you work at it you will improve.