Glute muscles do more than fill out the seat of your pants. Strong glutes help you walk around all day long and are vital to runners for keeping the pelvis stable. Without strong glute muscles you're at risk of developing shinsplints, iliotibial-band injury, Achilles tendinitis and runner's knee. When you work on building muscles in your butt with squats, you'll see and feel the evidence that they're working.
Feel the Burn
When you bend your knees to sit down on a chair, your glutes engage to help lower you and keep you balanced. When you perform a squat, you're going through a similar motion, but to a deeper degree. You'll know that your glutes are not only engaged but working when you squat down low enough to feel the tension in your butt and when you've done enough reps to feel a burning sensation in your glute muscles.
In the world of muscle building, squats have a deserved reputation for beefing up the butt. If that happens to be a body part that doesn't need more mass, you should modify your workout so that your glutes get enough exercise to tone but not build up. ExRx.net recommends doing more reps with lower weight, and bringing your feet in for a stance that isn't as wide as shoulder-width. Descend only halfway instead of going all the way down. Alternatively, instead of doing squats, substitute one compound exercise -- such as leg presses -- for the quads and the glutes, and then perform an exercise that isolates the quads, such as a leg extension.
Whether you perform squats with weights or only use your body weight for resistance, there's a proper form you should keep in order to ensure your glutes get a good workout. Stand with your feet shoulder-width apart. You can do squats with your feet closer together, but the narrower your stance, the more your quads will work and the less your glutes will work. Bend at your knees and hips to slowly lower yourself down as if you were going to sit. Concentrate on keeping your back straight and your head up. Descend far enough to feel the pull in your glutes. Your hips and knees will be fully bent. Straighten your knees and hips to come back to the starting position.
Basic squats will work your glutes, but when you're looking to single them out, Blackfoot, Idaho-based personal trainer Matt Siaperas recommends doing a one-legged version of the exercise. They're done by standing on one leg with your opposite leg lifted and extended in front of you. Keeping your shoulders back and your back straight, bend the knee of your supporting leg to descend into a squat, keeping your knee over your ankle as you go. You can hold your arms out in front of you to help with balance, if you need to. At first you may want to do shallow squats and eventually build up to deeper squats as you get better at doing them. The deeper you go, the more you'll feel it in your posterior.