Traditionally, you learn to squat from top to bottom, but as we mentioned in our squat primer
, many variables can limit your ability to squat well or to depth. For some, bad flexibility in the upper back, ankles, hips, and calves are to blame, but it’s also insufficient practice. These drills help you work on both.
Source: LifeHacker – Learn to Squat Better by Practicing the Movement Backwards