One of the most informative screens we take golfers through is the Overhead Deep Squat test.  To perform a functional Overhead deep squat, you need to have a combination of mobility and stability from head to toe.  You need to have adequate mobility at the ankles, knees, hips, thoracic spine, and shoulders as well as a strong posterior chain to hold the position.  Limitations in any of these areas can prevent you from performing a functional overhead deep squat.  If you are unable to perform the overhead deep squat there is a 99% chance you will have a loss of posture during your golf swing, generally early extension (moving toward the ball on the downswing) or a flat shoulder plane.

1. Upper torso is parallel with tibia or towards vertical
2. Femur is below horizontal
3. Knees are aligned over feet
4. Feet are pointing forward (not flared out)
5. Dowel/Club is aligned over feet