Gluteus Maximus – Functional Anatomy

Overview

The gluteus maximus is a large flat muscle on the posterior hip. It is the largest muscle in the human body. It is seen as one of the distinctive human features as it is larger and more developed than other mammals, including apes.

Origin

• bony attachments of the posterior crest of the ilium, sacrum, and coccyx
• the sacrotuberous ligament
• aponeurosis of the erector spinae
• posterior portion of the gluteal aponeurosis

Insertion

• gluteal tuberosity
• lateral proximal tibia via iliotibial tract

The deep fibers of the gluteus maximus insert on the gluteal tuberosity and IT band. However, studies vary on the superficial fibers. Some say that only the upper fibers insert into the IT band and all the lower insert into the gluteal tuberosity. Others say that all superficial fibers insert into the IT band.

Function

• extension of the hip
• stabilization of the knee
• external rotation of the hip

Most references state that the gluteus maximus extends the hip joint through the gluteal tuberosity and stabilizes the knee through the iliotibial band. They largely agree that it externally rotates the hip joint through the lower fibers. It is considered a weak abductor through the upper fibers and a weak adductor through the lower fibers, depending on the position of the gluteal tuberosity.

Innervation

• Inferior gluteal nerve
• dorsal branches of the ventral rami of L4, L5, S1
• S2 spinal nerves

Functional Considerations

Research conclusions on this muscle vary and, at times, seem contradictory:

• Some studies state that it is large because it maintains an erect posture. Other studies show it to be inactive while standing.
• One electromyographical study shows that the gluteus maximus is most active in side plank abduction, yet most anatomy sites consider it to be a weak abductor.
  
  Other conclusions were:
• females exhibit greater GM excitation than males in all exercises
• unilateral exercises exhibit greater excitation
• bracing abdominal muscles increase excitation.

Anomalies, Etc.

Like the IT band, I find contradictory studies more than finding studies that talk about anomalies. Also, it seems easier to find studies about differences in innervation than structural anomalies.

The deep fibers of the gluteus maximus insert on the gluteal tuberosity and IT band. However, studies vary on the superficial fibers. Some say that only the upper fibers insert into the IT band and all the lower insert into the gluteal tuberosity. Others say that all superficial fibers insert into the IT band.

Cranio Cradle Cup

This mug has classic, colorful illustrations of the craniosacral system and vault hold #3. It makes a great gift and conversation piece.