The biggest muscle you have
Your gluteus maximus is the largest muscle in your whole body. You have one on each side.
Gluteus comes from an old Greek word for the bottom. Maximus is Latin for 'biggest.' So its name means 'the biggest bottom muscle.'
Two smaller ones hide underneath: the gluteus medius (middle-sized) and the gluteus minimus (smallest). Big, medium and small, like the three bears' chairs!
Stand up!
Try it: sit on a chair, then stand up without using your hands. Your glutes just lifted most of you up.
Your glutes pull your thigh back and straighten your hip. That's the move for standing up from sitting or from a squat.
Try it: stand up tall and put your hands on the sides of your bottom. Squat down a little, then stand back up. Feel the muscles squeeze?
Stairs, hills and jumps
Here's a surprise: when you walk on flat ground, your gluteus maximus only works a little.
It does its big work when you climb stairs, walk up a hill, run fast or jump high.
That's why your bottom can feel tired after a long hike up a mountain.
Balance helpers
The gluteus medius, on the side of your hip, keeps your hips level when you stand on one foot.
Try it: stand on one leg and put your hand on the side of your hip. Feel the muscle hold you steady? Every step you take, it does this for a moment.
Why are ours so big?
Scientists think people have such big bottom muscles because we stand up straight and run on two legs.
Your glutes keep your body from tipping forward each time a foot lands while you run.
Chimpanzees, our close animal cousins, mostly get around on four limbs, and their bottom muscles are smaller for their size.