Photo Study of Novak Djokovic's Strokes

Here we see the moment just before the culmination of the kinetic chain on Djokovic's serve. His powerful upward leg thrust has lifted him off the ground, his upper body has largely straightened from its arch and rotated toward the net, and his arm has risen at the shoulder and straightened at the elbow. All of this energy is about to make his wrist whip forward and upward, bringing the racquet with it at great speed. The racquet is approaching the ball edge-first at the moment, but natural pronation of the forearm will turn the string bed much more toward the net at the point of contact.