Latissimus dorsi muscle
The latissimus dorsi muscle is a muscle that sits behind the rib cage, and extends up to the arm pit. When contracted, it pulls the arm down and back while rotating it inward. The muscle also plays a role in lateral flexion, and extension of the lumbar spine.
Anywhere between four to eight thoracic vertebrae connect to the latissimus dorsi, depending on the individual. In some cases, muscle fibers can reach the crest of the ilium at the top of the pelvis. The eighth, seventh, and sixth cervical nerves supply the latissimus dorsi by way of the throracodorsal nerve.
Exercises which affect the latissimus dorsi are dumbbell-rows, pull-downs, chin-up, pull-ups, and dead lifts.
Heart patients who suffer from low cardiac output, and who are not considered candidates for a heart transplant can undergo a procedure in which the latissimus dorsi is wrapped around the heart. Electro-stimulation is then used to achieve synchrony with the ventricular systole. This procedure is known as a cardiomyoplasty, and may help support a failing heart.