Gluteus maximus

What it is

The big, superficial muscle of the buttock, and by mass the largest single muscle in the human body. The quadriceps femoris is bigger, but that is a group of four muscles rather than one.

It is coarse-grained and thick, with fibres running diagonally downward and outward. It takes origin across a wide area at the back of the pelvis — the outer surface of the ilium behind the posterior gluteal line, the back of the sacrum and coccyx, the sacrotuberous ligament, and the thoracolumbar fascia.

Its insertion is the part worth knowing, because it surprises people: most of the muscle does not attach to bone at all. The greater part of its fibres end in the iliotibial tract, the thick band of fascia running down the outside of the thigh to the tibia. Only the deeper fibres of the lower portion attach directly to the femur, at the gluteal tuberosity. So a large share of what this muscle does is transmitted through fascia, past the knee, rather than pulling directly on the thigh bone.

It is supplied by the inferior gluteal nerve.

What it does

Its main job is hip extension — driving the thigh backwards relative to the pelvis, or, when the foot is planted, driving the pelvis and trunk upright over the thigh. That second version is what you are doing every time you stand up out of a deep squat.

It is also a strong external rotator of the hip, turning the thigh outward.

Its fibres do different things depending on where they sit. The upper fibres, running above the hip joint's axis, assist in abduction; the lower fibres assist in adduction. This is why describing it as one muscle doing one job is always slightly wrong.

The fact worth carrying away: it is largely quiet during ordinary level walking. Its activity rises sharply with running, stair and hill climbing, rising from a deep squat, and anything explosive. This is consistently observed in the electromyography literature. It is a muscle for high-force hip extension, not for locomotion at a stroll.

What loads it

Movements where the hip is extending under real resistance, and especially where it is extending from a deeply flexed position — the bottom of a squat, the drive out of a lunge, the top of a hinge.

The goblet squat loads it through the range where the hip is most flexed, which is where hip extension demand is highest.

Note what is not claimed here: that any of these is the best movement for this muscle. That question is usually answered with surface EMG comparisons, and those measure electrical activity over a short window rather than the thing people actually want to know, which is what changes over months. The honest position is that several movements load it well and the evidence does not cleanly rank them.

What is commonly got wrong about it

That it is asleep. "Glute activation", "gluteal amnesia", "dormant butt syndrome" — the idea that this muscle has forgotten how to fire and needs waking up with a band before you are allowed to train. Muscles do not forget. A muscle can be weak, and it can be used less in a movement than you assumed, and both are addressed by loading it. The clinical picture the phrase borrows from — genuine inhibition after injury or surgery — is real, specific, and not what is being sold in a warm-up video.

That it is trained for its appearance. The shape of the buttock is set by the muscle, the fat over it, and the pelvis under it, in proportions you do not control and cannot select. The reason to train hip extension is that hip extension is how you climb, run, lift and stand up.

That because it is quiet in walking, walking is not exercise. It is not the conclusion. Walking is excellent and it simply loads other things.

That "squats are the glute exercise". A common claim with more confidence behind it than evidence. See above — the ranking question is not settled, and both squats and hinges load it substantially.