Powerful forehand of the American Jack Sock in his first-round match during the 2010 US Open - Flushing Meadows - New York - USA - September 2010 - follow through with perfect long-axis pronation of a helix form.
Powerful forehand of the American Jack Sock in his first-round match during the 2010 US Open - Flushing Meadows - New York - USA - September 2010 - follow through with perfect long-axis pronation of a helix form.