The backswing generates racquet speed leading up to contact. The contact point is brief, lasting only 2-3 milliseconds, but it is the swing segment that directs the ball. The follow-through is the natural extension of every swing that allows the arm and racquet to decelerate to prevent injury. Players can also use the Direction Doctor to warm up their strokes, while better visualizing and feeling the point of contact relative to the body. The Direction Doctor is a remarkable tool to gain a better feel for racquet head acceleration, since the added mass of the device helps the racquet head accelerate and increase its momentum through the area of contact. Beyond just warming up and shadow swinging, use on court by swinging a few times with the Direction Doctor and then hitting balls. Switch back and forth until you experience the same sensation of an accelerated swing and lengthening through contact in both situations. Use for any stroke. The Direction doctor comes in two halves for easy assembly.