The gluteus maximus is the largest muscle in your body, and its primary job is extending your hip, meaning it drives your thigh backward and propels you forward. But it does far more than that. It stabilizes your pelvis, helps control your trunk, rotates your leg outward, and connects your lower body to your upper body through a web of connective tissue. It’s the reason you can stand up from a chair, sprint, climb stairs, and stay upright when carrying something heavy.
The Main Movements It Controls
Hip extension is the headline act. Every time you push off the ground while walking, stand up from sitting, or drive uphill on a bike, your gluteus maximus is shortening to pull your thigh behind your torso. It’s the most powerful hip extensor you have, and it shares that workload with your hamstrings.
Beyond hip extension, the muscle also externally rotates your leg, turning your knee and foot outward. This matters more than it sounds: external rotation helps keep your knee aligned over your foot during squats, lunges, and single-leg movements. Without enough rotational control from the glutes, your knee can collapse inward, which increases stress on the ligaments and cartilage inside the joint.
The upper fibers of the gluteus maximus also assist with abduction, pulling your thigh away from your body’s midline. This is a secondary role (the gluteus medius handles most of that job), but it becomes important during activities where you’re stabilizing on one leg.
Why It Matters for Core Stability
Most people think of the core as the abs and lower back, but the gluteus maximus is a critical part of the system. It attaches into a diamond-shaped sheet of connective tissue called the thoracolumbar fascia, which also connects to your deep back muscles, your obliques, and even your latissimus dorsi on the opposite side of your body. This creates a diagonal sling from your left glute to your right shoulder (and vice versa) that transfers force across your trunk every time you move.
This cross-body connection is not just theoretical. Research has shown that contracting the lat on one side increases stiffness in the lower back and changes the resting position of the opposite hip, pulling it into slight external rotation. During running, this diagonal system is what coordinates the opposite-arm, opposite-leg swing that keeps you balanced. Your right gluteus maximus fires in tandem with your left lat to stabilize your trunk against the rotational forces of each stride.
The gluteus maximus also plays a direct role in stabilizing the pelvis, particularly during trunk rotation or any time your center of gravity shifts. When you twist to throw a ball, carry a heavy bag on one side, or simply walk on uneven ground, the muscle helps prevent your pelvis from tilting or rotating out of position.
Walking vs. Running: A Dramatic Difference
Here’s something that surprises most people: the gluteus maximus is relatively quiet during flat walking. It activates mainly around heel strike to prevent your trunk from pitching forward, but for steady, level walking it doesn’t need to work very hard. Your hamstrings and passive momentum handle much of the job.
Running is a completely different story. At moderate running speeds (12 to 14 km/hr), gluteus maximus activation jumps to roughly 36% of maximum effort in men and 56% in women. Three things about running explain this spike. First, each stride has an aerial phase where both feet leave the ground, which means you land with much higher impact forces. Second, your trunk leans forward about 10 degrees more during running than walking, so the glutes must work harder to keep you from folding at the hips. Third, the faster pace demands more explosive hip extension to propel you forward.
This difference between walking and running is a big deal for anyone recovering from injury or trying to build glute strength. Walking alone won’t challenge the muscle much. Activities that involve more forceful hip extension, like stair climbing, running, or resistance training, are what truly load the gluteus maximus.
Why It’s So Much Bigger in Humans
Compared to our closest primate relatives, the human gluteus maximus is enormous. It makes up about 18% of total hip muscle mass in humans, versus roughly 12% in chimpanzees and 13% in gorillas. Relative to body mass, it’s about 1.6 times larger in humans than in chimps. The upper portion of the muscle expanded significantly during human evolution, while the lower portion that other primates use for tree climbing was lost.
Scientists have proposed three explanations for this. One is that early bipeds needed a reorganized gluteus maximus to climb while walking upright, since the muscle’s orientation changed when the pelvis tilted for two-legged posture. A second theory focuses on foraging: digging, throwing, and using tools require trunk stabilization against forward-bending forces, which the gluteus maximus is perfectly positioned to provide. The third, and perhaps most compelling, explanation is endurance running. Humans are exceptional distance runners among mammals, and the high demands running places on hip extension and trunk control may have driven the muscle’s expansion over millions of years.
What Happens When It’s Weak
Because the gluteus maximus connects to so many structures, weakness doesn’t just show up as a “weak butt.” It cascades. When the muscle can’t adequately extend the hip during walking or running, other muscles compensate. The hamstrings take on extra hip extension work, making them prone to strains. The lower back extensors pick up trunk stabilization duties, which can contribute to chronic low back pain.
A classic sign of gluteus maximus weakness is a visible change in gait: the trunk lurches backward at heel strike as the body tries to move the center of gravity behind the hip joint, reducing the demand on the weak muscle. You might also see excessive forward lean during squats, difficulty rising from a deep chair without using your hands, or knee collapse during single-leg activities like going down stairs.
Because the muscle is part of the diagonal sling connecting to the opposite shoulder, weakness on one side can also show up as poor rotational control. Throwing, swinging a golf club, or even walking with a natural arm swing all rely on force being transmitted cleanly through this system. A weak link at the glute disrupts the entire chain.
Best Exercises to Strengthen It
A study commissioned by the American Council on Exercise tested multiple exercises for gluteus maximus activation using surface sensors that measure electrical activity in the muscle. Nearly all compound lower-body exercises produced similar recruitment levels, but two stood out: the quadruped hip extension (often called a donkey kick) and the traditional squat. The quadruped hip extension is notable because it’s a bodyweight exercise that isolates hip extension, and it can be made progressively harder with ankle weights or resistance bands.
In practical terms, any exercise that involves forceful hip extension under load will train the gluteus maximus effectively. Squats, deadlifts, hip thrusts, lunges, and step-ups all qualify. The key variable is depth and load: the muscle is most active when the hip is flexed (bent) and has to extend against resistance, which is why deep squats and full-range hip thrusts tend to be more effective than partial movements. For people who sit most of the day, even simple exercises like glute bridges and the quadruped hip extension can begin to reverse the deconditioning that comes from prolonged inactivity.