The hamstrings are a major group of muscles in the upper leg. Sports and every-day activities can leave the muscles tight from use and in need of a good stretch.

Some coaches, trainers and textbooks recommend stretching before and after your workout because it can help your performance and reduce the risk of injuries.

External rotation is also known as lateral rotation. The muscles that rotate the shoulder include the teres minor, infraspinatus and posterior deltoid. When the opposing muscles that internally rotate the shoulder are tight, they limit the ability of the external rotators to rotate the shoulder outward.

Calves often receive less attention than your thighs as areas to exercise, but they provide essential support to your lower body and are used in a range of activities, including running, bicycling and jumping.

The onset of shoulder pain can be related to an injury or to the overuse that occurs with repetitive activities, such as those you might perform in sports, exercise and manual work or household tasks. Injury or overuse of the shoulder joint can damage the ligaments, tendons and muscles in the shoulder.

Gentle stretching improves your circulation, range of motion and flexibility. There are many muscles involved in moving your hips, including your glutes, hip flexors and adductors. If your hip muscles are tight, they can contribute to back pain. Some easy stretches will help you loosen the muscles in this area.

Some types of stretching, including movement-based dynamic stretching, can help warm up your body and prepare for physical activity. You might experience a feeling of warmth or tightness while stretching, but sharp pain indicates that something isn’t right.

The posterior cruciate ligament is a strong cord of tissue that connects the femur to the tibia. This ligament is behind the knee. Stretches can help keep it flexible and prevent injury. Stretches lengthen the hamstrings, which run down the back of the thighs to the knee area.

Stretching to emphasize flexibility should be part of a comprehensive exercise program. As you age, your joints and muscles can become stiff. Stretching helps to loosen these muscles, reducing pain and inflammation in the body, which is particularly helpful if you suffer from osteoarthritis.

Almost everyone has heard that they should "feel the burn" when exercising, but if the burn is due to overstretching, it's never a good sign.

The pectoralis minor is a small, triangle-shaped muscle located on the outer side of your upper chest. It connects your third, fourth and fifth ribs to the top of your shoulder blade and functions to stabilize the shoulder blade.

If you hear or feel a snapping, popping sound from your hip when walking or standing up, you may have snapping hip syndrome. The snapping is the result of a muscle, tendon or muscle fibers moving over the bony hip points on the front, back and outer surface of the thigh.