Perhaps it's a testament to the power of yoga that so many spin-offs have emerged—dozens since it originated some 6,000 years ago. There's laughter yoga, which turns humor into a healing power, AcroYoga, which revolves around flying, and hot yoga, taught in a 105-degree studio. Even naked yoga is catching on, described by followers as a therapeutic way to burst out of the confines of clothing.
Research bolsters the claims made for the trend: Yoga protects the brain from depression, an August study found; three sessions per week boosted participants' levels of the brain chemical GABA, which typically translates into improved mood and decreased anxiety. "People who have disorders like depression and anxiety can definitely benefit from yoga, because it returns [GABA] levels to the normal range," says study author Chris Streeter, an assistant professor of psychiatry and neurology at Boston University School of Medicine. Streeter says yoga can be used to complement—not substitute—drug treatment for depression.
Past research has explored yoga's effect on epilepsy, heart disease, cancer, and multiple sclerosis, among other conditions. A 2004 Yale University School of Medicine study, for instance, found that people who practice yoga reduced their blood pressure, pulse, and risk of heart disease. The health benefits likely come about—at least in large part—because yoga helps people better manage stress, says Janice Kiecolt-Glaser, a professor with the Institute for Behavioral Medicine Research at Ohio State University College of Medicine. "Yoga has a meditation component that is not true of other exercise. That aspect makes a difference," she says.
Other reasons to give the "warrior" or "downward-facing dog" poses a try: Yoga can increase strength, endurance, balance, and flexibility. Some types, like Ashtanga, are even vigorous enough to count as cardio workouts. Which type is most beneficial? "That depends on each individual person," says Streeter. What eases one person's back pain may do nothing for another. Here's a look at some of the more popular yoga varieties, what they involve, and their purported health benefits.
Ashtanga yoga. The fitter you are, the more likely you'll enjoy Ashtanga yoga, which revolves around repetition of athletic poses and leaves almost no time for catching your breath. The vigorous sessions involve standing and seated poses, back bends, and inversions—holding the head below the heart. You won't build bulky muscles, but you will increase muscle density. "Advanced practitioners look like Olympic athletes," says Lori Brungard, who teaches Ashtanga in New York City. "It's a very intense form of yoga, and because it's so demanding, it does require consistent, steady, regular practice to see the benefits." She recommends five to seven hour-long sessions per week.
AcroYoga. If yoga married gymnastics and circus art, you'd get this gravity-defying breed. First practiced in San Francisco six years ago, AcroYoga has seven elements, including Thai massage, therapeutic flying, and partner acrobatics. One person, the base, lies on the ground and uses his arms and legs to support a flyer. While suspended, the flyer twists into a series of positions—including the "folded leaf," hanging upside down on the feet of your partner. AcroYoga tones and loosens: "It's really great for people with back problems—you're opening your body without strain and without forcing it, and with the support of another person," says Vanessa King, a Washington, D.C.-based AcroYoga instructor. "You go from a Thai massage to the greatest activity of being lit up and energized in an acrobatic pose."