Photo Study of Novak Djokovic's Strokes

You can see much of the kinetic chain of a semi-open-stance forehand at work here. The forward and upward push from the legs isn't visible, but the rotational energy generated by Novak's upper body turning toward the net is clearly displayed by his shirt. The legs and torso have brought the arm forward, but still lagging behind is the racquet. The racquet's inertial lag stretches the forward-facing side of the forearm, and at the culmination of the kinetic chain, the elasticity in the forearm combines with all of the energy from the larger parts of the body to whip the wrist and racquet forward with the tremendous velocity that generates a world-class power forehand.