The front squat was frequently used when weightlifting was more popular. At present, it is most often considered inferior to the classic squat. In many respects it is, but it also has some unique benefits. The front squat is a great exercise for development of the quads and for use as a preparatory exercise before doing the squat and other exercises.
Because the weight is held in front of the body the front squat is effective in strengthening the knee joints. Perhaps its greatest value for many athletes is that it helps to keep the lower back in its normal lordic (slightly arched) position. This is one of the most troublesome areas when doing the back squat..
Execution is the same as in the basic squat, but because of the weight being held high on the chest, the trunk remains slightly more vertical. If you incline the trunk to a 45 degree angle it becomes extremely difficult to hold the barbell in place. Thus because of the more upright trunk position the exercise is ‘easier’, but still requires ample flexibility in the hips and knees.
During execution be sure to keep your weight evenly distributed on the soles of the feet. Do not let your heels rise since this will throw greater stress on the knee joint, which can be dangerous. If you cannot keep the heels down, stop your descent at the point where your weight starts shifting forward onto the balls of the feet
If you find the front squat more difficult than the back squat because of positioning and balancing of the bar, you should use lighter weights until you become more familiar with the exercise. In addition, you should work on developing greater back strength to hold the spine in proper position together with sufficient flexibility in your ankle, knee and hip joints.
Be sure that you hold your breath on the descent and ascent until you pass the sticking point at which time you exhale. This gives you greater control and makes it possible to do the exercise properly. For example, when you hold your breath, it firms (makes rigid) your rib cage.
The breath holding and rigid trunk is needed to transmit force from the legs to raise your body and the bar. If you did not hold your breath, your chest would “collapse”, making the lift more difficult and perhaps leading to injury.
For more information and description of the front squat exercise see Biomechanics and Kinesiology of Exercise.