Your quadriceps are located on the front of your thigh. Their job is to extend your knee and flex your hip. They are made up from four muscles: rectus femoris, vastas lateralis, vastas intermedialis and vastas medialis. These four muscles share a common insertion point in the quadriceps or patella tendon.

Your esophagus stretches down from the back of your mouth to your stomach. It has a soft lining surrounded by muscle that helps push little lumps of food to your belly. A low or acidic pH in your esophagus can cause damage to the lining.

If you notice pain while stretching your right arm, it’s likely you have an arm strain or sprain. The symptoms of strains and sprains are similar, but they affect different parts of your anatomy. Always consult with your doctor for a proper diagnosis and treatment of the pain in your arm.

If you experience both lower back and hip pain, chances are they’re related. In some cases, hip pain is a manifestation of a chronic back problem, just as lower back pain may be a result of tight hamstrings, weak abdominal muscles or inflexible hips.

The hamstring is a dense muscle that tends to get tight, particularly if you spend many hours working on a computer. Knots may develop in spots where muscle fibers have actually bonded. Think of a knot as a balled-up rubber band. If you pull on it, the knot becomes more compact.

Hunching at a desk, sleeping in an awkward position and overdoing a workout can all lead to back pain. If the pain is intense, it can limit your range of motion. Along with over-the-counter pain relievers, warm baths and massage, stretching can help relax your back and alleviate pain and stiffness.

Sports massage focuses on optimizing muscle, tendon, ligament and joint health in order to prevent sport injuries or promote healing after an injury has occurred. It is commonly used before or after sporting events, or during training.

Trauma tremors are compulsive or involuntary trembling that occurs after a shock or scare. Also known as the jitters, knocking knees and shaking like a leaf, such tremors are the body's way of releasing excess energy and stress.

Flyers perform many types of movements within a stunt. From turning and bending to twisting and contorting, flexibility is important for any flyer. Without a solid stretching routine, you are at risk of injury from muscle tears.

The lateral retinaculum is a ligament that helps hold your patella, or kneecap, in place. When the knee moves slightly out of place or becomes tilted in the joint, it can cause tension and pain in the lateral retinaculum. Stretching this ligament keeps the patella in place and the ligament healthy.

The lumbar part of your spine is your low back, and it consists of five vertebrae which are referred to as L1 through L5. The discs between these vertebrae act as shock absorbers, and they also bear a significant amount of your weight.

Your brachialis is hidden beneath the biceps. Your brachialis is the only true elbow flexor because it attaches to your ulna, the forearm bone that doesn't rotate, as opposed to the radius, which does.