To improve in a sport, you need to commit to it, right? Sure. But as most top athletes can attest, cross-training is essential. Stick to one game and you'll let key muscle groups fall by the wayside while risking burnout. Mix up your training and you'll keep your body balanced and your mind fresh. Exhibit A: Adam Craig, 27-year-old Olympic mountain-bike racer and former competitive kayaker and skier. Last July, Craig defended two titles at the U.S. mountain-bike nationals. His secret: a six-day-a-week training program that includes lots of time off the saddle. We asked Craig how his various sports benefit one another—then fact-checked his answers with Dr. Michael Joyner (see footnotes), a leading exercise researcher at the Mayo Clinic.

"I used to have lower-back pain. In 1998, I learned how to paddle, and I haven't had a back problem in a bike race since¹. When I'm home, in Bend, Oregon, I get out a few times a week for a paddle on the Deschutes River. I'll go for a bike ride in the morning, take a nap, then paddle in the afternoon². Someone told me I would have ridden better at the Beijing Olympics if I hadn't been dicking around kayaking [Craig finished 29th in a field of 50]³. But I stick to the ideology that variety is good⁴.

"In winter, I ski every day⁵.

You can't mountain-bike much, so you're training on a road bike, and you lose the central-nervous-system stimulation that you get from picking a line through a tree run⁷. Carving a turn on skis with your torso vertical is exactly how you ride a mountain bike.

"I used to compete as a whitewater kayaker, and I was a ski racer in high school: nordic, alpine, GS, and freestyle. I don't do that anymore—I've got enough competition in my life⁷. I ski and paddle to get away."

FOOTNOTES: THE EXPERT WEIGHS IN

1. Kayaking is a natural way to train your core and upper body. Reduced lower-back pain is consistent with this.

2. Remember that biking is this guy's job—we're not talking about an average person doing this to stay fit.

3. To attribute one outcome in a single event to somebody's training program over a number of years is a little nutty.

4. There is no one right method. Craig found a way to keep himself psychologically fresh, and that's great.

5. You want to be active every day. If Craig keeps his aerobic power up, that will help keep his quads strong.

6. This is a reasonable way of saying that, like mountain biking, skiing tests your balance and forces you to move in a coordinated way.

7. Very wise. Being able to ration your competitive energy for the most important events is key.