"Unconscious Reactions to Out-of-Balance Situations
When the body is out of balance, the brain immediately makes a subconscious adjustment.  To demonstrate how the upper body reacts when the player performs a skill with the lower body out of balance, think again about riding a bike.  When the rider puts their arm to the side, the body immediately and unconsciously adjusts to make sure the rider does not fall.  In sports, the same thing happens with the upper on a daily basis."

"The Athletic Position
Overview. The "Athletic Position" is a common thread throughout sports. All skills begin with an "Athletic Position" or a modified "Athletic Position."...
The Athletic Position Mechanics. Head - up... Shoulders - depending upon the action, the shoulders are either square to the target or at a right angle to the target... Feet - shoulder width apart... Knees - bent to the point that the knee caps are over the player's toes... Chest - over the knees... Waist - slightly bent to bring the chest over the knees... Back - slightly arched... Hands - to the side of the body."