The Latissimus Dorsi muscle (commonly called the “Lats”) is the broadest of the back muscles. It covers the width of the lower and mid back and goes up along the lower aspect of the scapula (shoulder blade) and connects to the inner part of the upper arm, just below the shoulder joint. Because the Latissimus Dorsi covers such an expanse part of your body, it often affects movements in the back, shoulder, and arms. It is a primary muscle in activities such as pull-ups, rock climbing, swimming, throwing a ball, shoveling, and even chopping wood.
The function of the Latissimus Dorsi muscle is to:
internally (medially) rotate the shoulder
extend the arm behind you
adduct the arm toward the body.
I jokingly like to call it the handcuff muscle. If you do all the actions, it will place your arms behind your back, as if you were being handcuffed.
The Lats also assist in doing the following functions:
extension and flexion the trunk
lateral flexion of the trunk (side bend)
anterior and pelvic tilt
depression of the scapula
protraction of the scapula
inhalation and exhalation movements of the ribcage
An injured Latissimus Dorsi can be felt in the shoulder, back, or in the upper or lower arm. Latissimus Dorsi pain is usually caused by over use, using poor techniques, or not warming up the muscles before activity. It can also be caused by poor posture and slouching. Pain will feel worse when the arm is reached forward or extended. It is best to practice the RICE protocol if you feel like you might have injured your Lats. Rest. Ice. Compress. Elevate (sit upright with a pillow behind your back and shoulder blades). Alternating heat and ice can be helpful, as well as massage to help relax and loosening the tight or overworked muscle.
Once you are no longer in the acute stage, gentle stretches are encouraged to regain range of motion of the Latissimus Dorsi. Your doctor or physical therapist can also recommend some strengthening exercises that you can do at home to help prevent further injuries of your Lats. In most cases, Latissimus Dorsi pain will go away on its own with rest, massage, stretching, and exercises that can be done at home.