Latissimus Dorsi: Antagonist, Action & Insertion

Instructor: Dan Washmuth

Dan has taught college Nutrition, Anatomy, Physiology, and Sports Nutrition courses and has a master's degree in Dietetics & Nutrition.

Do you know the insertion, actions, and antagonists of the latissimus dorsi muscle, a muscle frequently referred to as the ''lat'' muscle? If not, then you should definitely read this lesson.

Latissimus Dorsi

Have you ever watched the swimming events in the Summer Olympics or seen pictures of professional body builders? If you have, then you have probably noticed that swimmers and bodybuilders have very developed back muscles, especially the muscles located at the sides of their backs, right under their arms. In some athletes, these muscles are so big that they almost look like wings.

Bodybuilders, such as Arnold Schwarzenegger, have very developed latissimus dorsi muscles.

The muscles that are being described in these athletes are called the latissimus dorsi muscles, or lat muscles for short. The latissimus dorsi is a thin, wide, triangular-shaped muscle located at each side of the back, right under each arm.

The latissimus dorsi muscle (shown in red).
latissimus dorsi

Latissimus Dorsi: Insertion

The latissimus dorsi inserts or attaches to the humerus, the long bone of the upper arm. Specifically, this muscle inserts on the intertubercular groove of the humerus, also known as the 'bicipital groove'. This groove is an indentation on the humerus in which the large tendon of the biceps brachii is also found.

Latissimus Dorsi: Action

Several actions are performed by the latissimus dorsi, all of which involve moving the humerus around the shoulder joint. These actions of the humerus include:

  • Adduction: Pulling or bringing the humerus from a raised position down to the side of the body. Think about a swimmer performing the butterfly or free-style stroke. These strokes require the swimmer to pull their arms from above their head down to their sides, a motion called 'adduction'.
  • Medial/internal rotation: Rotates or turns the humerus in towards the center of the body. This occurs when a person crosses their arms in front of their chest.
  • Extension: Pulling or bringing the humerus backwards. This occurs when a person is walking and they swing their arm backwards as they stride forward.

Michael Phelps uses his latissimus dorsi muscle to adduct his humerus while he swims the butterfly stroke.

Latissimus Dorsi: Antagonist

An antagonist is a muscle that opposes the action of another muscle. Therefore, antagonists of the latissimus dorsi would be any muscle that opposes the actions of adduction, medial rotation, and extension of the humerus. The following chart describes the specific antagonists of the latissimus dorsi.

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