The benefits of cross-training have been well-known since Nike aired those "Bo Knows" commercials a generation ago: A combination of different activities conditions the entire body—not just specific muscle groups utilized for one sport—and prevents injury by allowing some muscles to recover while others are pushed. But only now are we starting to grasp the best way to put cross-training to use. A multisport routine can get you in the best shape of your life—in six weeks or less. All it takes is a month and a half of long workouts to build a base that’s strong enough to sustain you in the long run, with a much smaller time commitment.
The idea is rapidly gaining traction among athletes, but the principles of Burger’s do-less success apply to mortals too. With a solid fitness foundation, you can prep for a big event—a marathon, a century, even an Ironman—in far less time than most people realize. In Burger’s case, he was already fit, so now he no longer needs to invest hours each day to maintain his edge. In fact, he says, he stays competitive by "running just 45 minutes on weekdays and then doing a different activity for longer bouts on weekends."
The best plan of attack? Alternate short, strenuous workouts featuring different activities (see "How to Get More Out of Doing Less," below). "The key is intensity," says Bill Pierce, a founder of the Furman Institute of Running & Scientific Training and co-author of the training guide Run Less, Run Faster. "If you run hard one day, for instance, you can’t run hard again the next because those running muscles need to recover. But if you, say, cycle the next day instead, you can go hard again. Your cycling muscles will get an intense workout while your running muscles recover. So you’re able to prevent injury—and achieve total fitness in a lot less time."
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