Your longissimus thoracis is one of the three muscles of your longissimus, which in turn works with your iliocastalis and spinalis to form your erector spinae muscle group. These muscles are responsible for keeping your posture straight, stabilizing your spine and arching and flexing your back. A weak longissimus thoracis may cause back pain or poor posture, but this muscle can be worked out by exercises that stress either spinal extension or spinal stabilization.
The Longissimus Thoracis
The longissimus thoracis is the largest of the three longissimus muscles, stretching nearly the entire length of your back. The longissiumus muscle is one of the three subdivisions of the erector spinae muscle group, which runs down the length of your spine and is responsible for lateral flexion and spinal extension. The longissimus specifically controls the flexing and rotation of your neck and upper spine, and can be strengthened in one of two ways: spinal extension or stabilizing the back muscles in an isometric position.
Spinal Extension Exercises
Strengthening the longissimus thoracis via spinal extension requires exercises that push the muscle through its full range of motion. Because of its central location in the body, nearly every form of vigorous exercise will require the spinal muscles to contract and extend. Some examples of exercises that rely on spinal extension to work out the erector spinae are back extensions, swimming, rowing, pullups, pulldowns, deadlifts and cable rows. All of these exercises work your upper spine, using either weights, your body weight or the pull of gravity as resistance.
Spinal Stabilization Exercises
Spinal stabilization exercises move your longissimus into a contracted or extended position, then hold that position isometrically to build strength. Isometric exercises are those in which the muscle is contracted without moving at the joints, and often include stretching and holding the muscle as blood flushes through it. Examples of isometric stabilization exercises include the superman posture, the plank and several types of yoga poses. These exercises normally begin with you lying on the floor or across a stability ball, then extending your arms or legs outward. Your spinal muscles will contract to bring your shoulder blades together, and in holding this pose for a predetermined length of time, you can target and strengthen these muscle groups.
When performing spinal extension exercises such as deadlifts or back extensions, it's important to keep your spine as straight as possible. Slouching or arching the back can put pressure on different areas of the back and possibly lead to back pain or injury.
Always warm up and cool down before and after any exercise. Loosen up your back muscles by stretching and rotating your head, neck and lower back. Weight-lifting exercises should always be done under proper supervision, particularly when they involve your spine. Consult your doctor or physical therapist before starting any workout routine.