Samantha Stosur has won 23 doubles and three singles championships, including the 2011 U.S. Open. The Australian, a brand ambassador for USANA Health Sciences and an ASICS-sponsored athlete, has traveled the globe playing tennis since she was a teenager. "Packing suitcases isn't my favorite thing to do," Stosur jokes on her first day back in New York, five days before the 2012 U.S. Open. We spoke to her about the diet and fitness routines that lead her to victory.

How many hours a day do you spend training?

It depends on the time of year and what's coming up. Preseason, I do two to three hours' fitness each day, then a tennis session. As you get closer to a tournament, you drop back the fitness and concentrate on being on court, [usually about] three hours each day.

What's in your gym routine?

Weights, squats, lunges, chin-ups and a lot of core stability exercise. I do endurance on a bike. Preseason I'll do boxing sessions and swimming and indoor rock climbing. I try to do stuff that I can't do during tournaments; it makes it a lot more enjoyable to mix it up.

How do you protect your joints?

For any professional athlete, in the long run it isn't that healthy. ... I had Lyme disease four years ago -- the doctors told me I have to be wary of joint problems. Also, [instead] of pounding your joints on a treadmill, I use a bike or swimming to avoid extra wear.

What's your diet like?

It's not easy when you've got to eat out all the time. Restaurant food tastes fantastic, but I'm sure it's not all that good for you. I try to keep everything in moderation. You learn to find what works for you. I always keep my immune system going with vitamins as a backup. You have to be careful; since having Lyme [disease], I've become more aware. I listen to my body and what it needs.