Like beer and pizza, only healthier

Origin: Kimberly Fowler, a Nike-sponsored yoga athlete (who knew?), founded YAS Yoga & Spinning Center five years ago for the simple reason that she loved both forms of exercise. "Yoga is the athlete's secret weapon," she says.
Who's Doing It: Robert Downey Jr., Julia Roberts, Gabrielle Reese, and swarms of surfers, ultrarunners, and triathletes.
The Workout: Trendsetters at Fowler's Venice, California, gym combine two of the decade's hottest workouts into one fresh routine, pairing loud-and-proud spinning with relax-the-mind yoga. The 45-minute spinning sessions are divided into intervals that mimic sprints and climbs, and the whole thing is fueled by blaring, fast-paced music. Don't be surprised to hear primal exer-screams during peak efforts. After spinning, you'll hobble to the yoga studio, where YAS's Yoga for Athletes works the kinks out of tight hips, hamstrings, quads, and lower backs. The 30-minute yoga session is geared toward stiffer, stronger athletes, not human flexi-dolls, and they eschew Sanskrit, chanting, and anything that smacks of the New Age.
They Say: Fowler estimates that her spin sessions burn up to 800 calories. The rewards of yoga include improved circulation, flexibility, strength, and balance.
I Say: After a typical spin class, I generally leave with an endorphin high, sore legs, and a stiff lower back. Following it up with a yoga session releases lactic-acid buildup, stretches muscles, and allows me to enjoy that post-spin euphoria before rushing off into buzz-killing bumper-to-bumper traffic.
Where to Find It: YAS has one location, in Venice (go2yas.com; $15 per class). But similar classes are popping up at gyms nationwide, and anyone can try the combo with the Cy-Yo DVD ($25; cy-yo.com), which sandwiches a 40-minute spin class between ten-minute yoga sets.