Here's some more of her training routine:
During the off-season, Wozniacki puts in four to five hours on the court and another hour or two in the gym. On the court, the focus is building muscle memory. She repeats drill after drill, making the tiniest of adjustments until she has perfected her serve or return. Some days she’ll do more than 100 volleys from different angles and positions. In the gym, workouts start on the treadmill. An “easy” day may mean running seven miles in 45 minutes, while a “hard” day may entail four miles of sprint intervals.
[ via WSJ.com]