Great buttock

The gluteus maximus muscle is the most superficial and developed of the muscles of the gluteal region (66 cm 2 of section). It is covered by the superficial gluteal fascia and in an upright position it covers the ischial tuberosity (while in the sitting position it leaves it free). In relation to its origin two parts can be distinguished, one superficial and one deep. The superficial part originates from the external lip of the iliac crest, from the superior posterior iliac spine, from the thoracolumbar fascia (or lumbodorsal), from the posterior aspect of the sacrum and from the coccyx. The deep part originates from the wing of the ileum, behind the posterior gluteal line, from the sacrotuberous ligament (or sacroiliac) and from the fascia of the gluteus medius muscle.

These numerous bundles converge downwards to fit near the rough line of the femur. In particular, its proximal part radiates into the ileotibial tract of the fascia lata while the distal part is inserted into the gluteal tuberosity (lateral branch of the rough line of the femur).

The gluteus maximus is the most powerful muscle of the body (34Kgm for a shortening of 15 cm), the largest and of course the strongest (238 Kg). It consists predominantly (50%) of type I fibers (slow contraction), 20% of type IIa fibers (at an intermediate contraction speed) and 30% of type IIb fibers (fast contraction) .

The gluteus maximus muscle is not a strictly postural muscle, it is not much involved in walking but only in the forced extension of the hip as in running, climbing or lifting from a sitting position.

With its action it extends and rotates laterally (extraterrost) the femur.

Because of its different insertions it can work both as an adductor and as an abductor. The upper part (which radiates in the fascia lata) abducts, while the lower part (which fits into the gluteal tuberosity), the more developed of the two, gives.

It is innervated by the inferior gluteal nerve (L5, S2).

ORIGIN

Superficial part: from the external lip of the iliac crest, from the posterior superior iliac spine, from the thoracolumbar fascia (or lumbodorsal), from the posterior aspect of the sacrum and from the coccyx.

Deep part: from the wing of the ileum, behind the posterior gluteal line, from the sacrotuberous ligament (or sacroiliac) and from the fascia of the gluteus medius muscle.