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The Hill Sprint Workout

Andre Agassi won five Grand Slams after he turned 29. A big part of his late-career success was his legendary fitness, which included sprinting up a 320-yard hill 14 times a day, every day, at his peak. "Andre wanted something that had the same burn as long-distance running but was more specific to the running you do around a tennis court," says Gil Reyes, Agassi's conditioning coach. He got it with hill sprints.

Think of hill sprints – running fast uphill for five to 45 seconds – as a marriage between leg squats and track sprints. They recruit fast-twitch muscles that boost speed and pump legs with lactic acid, which ultimately improves fatigue resistance. Unlike flat running, hill sprints are done against gravity, building muscle more quickly with less impact.

"No matter your fitness goal, hill sprints can help you reach it," says Reyes. If you play basketball, sprints will get you up and down the court faster. If you run, they'll help you find another gear to kick to the finish line. If you play tennis, they'll give you three-set stamina and get you from baseline to net faster. And if you just want to be fit and lean, they'll do that, too, by creating an oxygen deficit that ups lung power and fires off fat. Launch Gallery >>

– Matt Fitzgerald