The strength of Isner's game is his serve, which has topped out at 149 mph. "I need to have as much energy as possible in my service games," says Isner, who relies on motion stretching and light weight training to keep his right arm strong. On defense, though, he picks his spots. Kind of. "If I'm up a break in a set, I can just ride out my serve," he says. "That doesn't necessarily mean that I'm tanking the return games, but it gives me the opportunity to conserve energy for the service game, knowing that I have that break in hand."
Tennis is not meant for the tall man. Its aerobic and kinesthetic demands, stressful enough for a 6-footer, could nearly break the 6'6" Isner. He hasn't broken yet because of the work he puts into his core: multi-planar-based stability exercises that are designed to strengthen his abs and lower back. "It's all stability for him," Morgan says. "If you have no core stability, momentum can take your body control away from you.
Isner counts meals, not calories. His target is three or four a day, with plenty of energy bars, berries and bananas in between—especially during changeovers. Save for pasta, "there's nothing I don't like," he says. He gets most of his carbs from brown rice and sweet potatoes. The nutrient-rich diet includes a steady dose of meat for protein and supplies Isner with premium fuel. Staying hydrated and keeping the electrolytes flowing limit the potential for cramping—which was once a recurring story line in his matches.
The Open is as much a mental game as a physical one. Decompressing off the court is particularly easy for Isner, 28, this time of year, what with football starting back up and all. (The Carolina Panthers and Georgia, his alma mater, are the teams he follows most closely.) Finding peace during a match, however, is tougher to practice. "You can't duplicate adrenaline," says Kyle Morgan, Isner's strength and conditioning coach. "When you release adrenaline and pressure and you're stressed, your heart rate is gonna get higher. We try our best, but we're limited in the situations we can re-create."
HEART, LUNGS AND LEGS
During the off-season Morgan puts Isner through a formidable circuit (which includes sled pulls, hurdles and a 200-yard dash) with the aim of allowing him to recover quickly from intense play. "A point can be one second long," says Morgan. "We might choose work-to-rest ratios that are going to mimic three games in a row. We'll work for five seconds and be off for 15, work for 20 and be off for 30. It's about getting his body used to working really, really hard at a high level for five seconds, and then resting to get his energy levels back up." Another priority is protecting Isner's knees; a sore left one slowed him for a stretch this summer. A prematch stretching routine that focuses on his glutes helps activate the muscles around the knee to better guard against injury.
DAVID WALBERG FOR SPORTS ILLUSTRATED