Squats work very well at toning and strengthening the quad muscles. Because squats require balance and core strength to maintain positioning, they are also effective in helping with stabilization.
Squats work both the knees and hips and are useful for strengthening the ligaments and tendons surrounding each. They also help prevent injury to the knees. Squats help with muscle coordination and in training the body for hip extension, which is a natural part of many sports. Because squats use a person's body weight, some people see them as safer than leg presses, which also work the same muscles but can cause lower-back issues.