THAT RODDICK HAS been entrenched in tennis's top ten for most of the past six years (at press time, he was still ranked sixth) without suffering serious injury is pretty solid proof of his commitment to off-court training. He has always been ahead of tennis's fitness curve. Though he's gone through a string of coaches, including, from 2006 until early this year, Jimmy Connors in the role of consultant (Roddick insists they parted amicably after Connors decided he didn't want to endure the travel obligations of the pro tour), he now seems to have settled into a groove with a team composed of his coach/brother, John, 32, and athletic trainer Doug Spreen, 38, hired away from the ATP in 2003.

On a remote practice court in Miami, the day before Roddick would face Federer, I watched Spreen dilute a sports drink, cutting it in half with water so that it "absorbs quicker." Roddick, Spreen said, has two things working against him when it comes to fitness. One is his size: At six-two and 195 pounds, he's taller and thicker than most top pros. The other is a higher-than-normal sweat rate. ("I'm disgusting," Roddick said, pausing to set up his own joke,

"Andy's work ethic is incredible," says his sports-performance coach. "Only a handful of tennis players come close to what he does off the court."

"which was a real problem with my personal life for a long time.") Because he's losing more fluids than his opponent, Roddick has to make a real effort to stay hydrated. "When I'm training I go through six, seven, eight liters of water just replacing what I need to. It's definitely more effort."

Out on the court, Roddick was blasting balls. "The forehand's coming off good today," he said to his brother. Roddick's forehand, like his serve, is among the best on the tour and requires both strength and resilience—more every year as players get stronger and faster. "If you're gonna hit 150 balls that much harder in a match, it takes that much more energy," Spreen explained. "And two guys hitting the ball harder at each other means that they've got to move that much quicker to get the ball. They have to be ready to play a more explosive game."

To this end, in 2005 Spreen enlisted the help of Lance Hooton, the Austin-based owner of Hooton Sports Performance Training, an outfit that focuses primarily on what Hooton calls "power-speed athletes." Hooton says Roddick was in excellent shape and, more important, eager. "I can go down a list of phenomenally gifted athletes who are not willing to learn," Hooton says. "Andy is the opposite of that. His work ethic is incredible. I only know a handful of tennis players who even come close to what he does off the court."

Still, some of Roddick's athletic skills were lacking, and his training had been focused on endurance. Hooton set about creating a regimen to build power and speed, particularly important for the world's hardest-serving player, whom Hooton calls "the Nolan Ryan of tennis." Hooton stepped up Roddick's weight training, implemented body-weight-resistance programs and plyometrics, and added sprint intervals. The intervals serve to increase his quickness and, as Spreen reminds me at another point, his recovery.

"If you're playing a service game, you go out and you play a 45-second point and you've got 25 seconds before you're serving again," Spreen says. "That's where you get into the interval training: sprint, recover, sprint, recover. You train the body to be stressed and to recover quickly from that stress."

Roddick says tennis's ephemeral off-season (more or less a month with Christmas sandwiched in the middle) is when he gets the opportunity to "build, build, build." Once tournaments get rolling, he plays so often that his fitness program is highly erratic. Hooton gives the team a number of options for light-, medium-, and high-intensity days and also plans for days on which Roddick should only jog and stretch. "You have to give yourself time to give your body a break," Roddick says. "I've become real particular about that. I have to have windows every couple of months where I can put my body back together." He also makes sure to have some non-tennis playtime, tearing around Texas's Lake Austin (where he's owned a home since 2003) on his speedboat and trail-running in a nearby wilderness preserve.

"People make fitness out to be this whole specific thing," he says. "But, basically, if you're willing to put in the hours and go through the grind, you're going to be OK."