Research proves it: the human body is designed for strenuous, long-haul adventure. Recent studies have even suggested that endurance running actually shaped the evolution of the human body. According to Harvard paleoanthropologist Daniel Lieberman, an author of many such studies and The Story of the Human Body, human beings "are fundamentally adapted to get exercise." But the gym is not enough. "There's nothing like the real thing," says Adam Chase, president of the All American Trail Running Association. The outdoors is simply more demanding. "When you're out on the trail, you have to dance through the rocks and routes." That translates into automatic interval training, which strengthens your heart by forcing it to learn to adapt to just about anything. Here's your guide to getting your heart in shape – and having fun while you're at it.
The low-impact, easy-on-the-joints nature of cycling lets you go for hours.
Quads, hamstrings, calves, glutes, and core work in concert.
Amp It Up
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Determine your cadence by counting how many times one of your legs rises in 15 seconds; multiply that number by 4. Berlinger suggests you ride at a 90-100 cadence for four minutes in an easy gear. Kick it up a gear and maintain the cadence for another minute. Do another four minutes at the original gear before going up two gears for another minute at 90-100. Keep pushing until you can't do a full minute at that pace.