Dr. Laskowski: The squat is a body resistance exercise that works the leg muscles. Specifically, the squat targets the quadriceps and the hamstring muscles. Strengthening these muscles can help protect your knees and boost your performance in a variety of sports.
Nicole Campbell: To do a squat, stand with your feet slightly greater than shoulder-width apart and your toes pointing ahead. Slowly descend, bending through the hips, knees and ankles. Stop when your knees reach a 90-degree angle. Then return to the starting position. You'll feel tension in your legs and buttocks.
When you're doing squats, keep your back in a neutral position. Don't flatten the curve of your lower back, and don't arch your back in the other direction. Make sure that your knees stay centered over your feet on the way down. Don't let your knees roll inward or outward. If you can't bend your knees to a 90-degree angle, simply go as low as you can. Use your arms for balance and support. Stop when you're fatigued or your form begins to suffer.
For most people, one set of 12 to 15 repetitions is adequate.
Remember, for best results, keep your back in a neutral position and your abdominal muscles tight during the exercise. Keep your knees centered over your feet on the way down. Also, remember to keep your movements smooth and controlled.