Gluteus maximus

The gluteus maximus is the main extensor muscle of the hip in humans. It is the largest and outermost of the three gluteal muscles and makes up a large part of the shape and appearance of each side of the hips. It is the single largest muscle in the human body. Its thick fleshy mass, in a quadrilateral shape, forms the prominence of the buttocks. The other gluteal muscles are the medius and minimus, and sometimes informally these are collectively referred to as the glutes.

Its large size is one of the most characteristic features of the muscular system in humans, connected as it is with the power of maintaining the trunk in the erect posture. Other primates have much flatter hips and cannot sustain standing erectly.

The muscle is made up of muscle fascicles lying parallel with one another, and are collected together into larger bundles separated by fibrous septa.

Structure

The gluteus maximus (or buttock) is the outermost muscle of the buttocks. It arises from connections to nearby structures in this area. It arises from the posterior gluteal line of the outer upper ilium, a bone of the pelvis, as well as above it to the iliac crest and slightly below it; from the lower part of the sacrum and the side of the coccyx, the tailbone; from the aponeurosis of the erector spinae (lumbodorsal fascia), the sacrotuberous ligament, and the fascia covering the gluteus medius (gluteal aponeurosis).

Function

The gluteus maximus straightens the leg at the hip; when the leg is flexed at the hip, the gluteus maximus extends it to bring the leg into a straight line with the body.

Society and culture

Training

The gluteus maximus is involved in several sports, from running to weight-lifting. A number of exercises focus on the gluteus maximus and other muscles of the upper leg:

Hip thrusts
Glute bridge
Quadruped hip extensions
Kettlebell swings
Squats and variations like split squats, unilateral squats with the raised foot positioned either backwards or forwards (pistols), and wide-stance lunges
Deadlift (and variations)
Reverse hyperextension
Four-way hip extensions
Glute-ham raise

In art

In cultural terms, the glutes are often considered a symbol of health and strength, and aesthetically appealing. They frequently feature in artwork which seeks to emphasise and celebrate physicality, and the ability to move dynamically and powerfully. They are usually shown to be efficiently proportioned and prominent.

Evidence of such depictions of the gluteal muscles extends from at least Ancient Greece to the modern day.

File:Javelin thrower Ancient Greece.jpg|An Ancient Greek javelin thrower represented on a vase, c. 520 B.C.

File:Statue B Riace Bronzes side view.jpg|An Ancient Greek warrior in bronze. Riace Bronzes, c. 450 B.C.

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Clinical significance

Functional assessment can be useful in assessing injuries to the gluteus maximus and surrounding muscles.

The 30-second chair-to-stand test measures a participant's ability to stand up from a seated position as many times as possible in a thirty-second period of time. Testing the number of times a person can stand up in a thirty-second period helps assess strength, flexibility, pain, and endurance,

Other animals

The gluteus maximus is larger in size and thicker in humans than in other primates. Specifically, it is approximately 1.6 times larger relative to body mass compared to chimpanzees and comprises about 18.3% of total hip musculature mass versus 11.7% in chimpanzees. Its large size is one of the most characteristic features of the muscular system in humans,

In other primates, the correlate to the human gluteus maximus consists of the ischiofemoralis, a small muscle that corresponds to the human gluteus maximus and originates from the ilium and the ligaments of the sacroiliac, and the gluteus maximus proprius, a large muscle that extends from the ischial tuberosity to a relatively more distant insertion on the femur. In adapting to bipedal gait, reorganization of the attachment of the muscle as well as the moment arm was required.

Running

The human gluteus maximus plays multiple important functional roles, particularly in running rather than walking. During running, it helps control trunk flexion, aids in decelerating the swing leg, and contributes to hip extension. During level walking, the muscle shows minimal activity, suggesting its enlargement was not primarily adapted for walking.