The follow through occurs after contact with the ball is made.
Here, the racket arm continues with internal rotation of the shoulder, pronation of the elbow and flexion of the wrist. The racket ends up pointing down toward the ground and you land on the front foot (Figure 1-12b).
The racket arm then adducts across your body (Figure 1-12c and 1-12d). The back foot comes forward, landing in the court going toward the net signifying the end of the serve (Figure 1-12d).
The muscles that adduct the racket across your body are the Pectoralis Major and Anterior Deltoid.
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Dr. Larry Van Such