Bikram yoga. Followers call it "hot yoga," because studio heat is cranked up to 105 degrees with 60 percent humidity—even in the summer. The 90-minute sessions revolve around a series of 26 postures, each performed twice. There are "spine twisting" and "toe stand" poses, for instance, and a "cobra pose"—legs and pelvis on the mat, back arched, and torso erect. Expect to burn between 350 and 600 calories in one class, while building stamina and endurance. Heat warms the muscles, allowing greater flexibility, says Kelly Schrader, who owns a Bikram studio in Grass Valley, Calif. "It's tremendously beneficial—especially for people who have joint injuries, inflammation, or conditions like arthritis," she says. "It boosts your overall health and immunity." Some advocates say hot yoga also helps flush toxins from the body, but doctors generally believe the body is more than capable of ridding itself of most harmful and waste products on its own. Prolonged time in a hot environment raises the risk of fainting and can be dangerous to those susceptible to heatstroke, like pregnant women, young children, and the elderly. If you're concerned, talk with your doctor before trying a class. And make sure to drink water frequently, while watching for nausea, dizziness, and the absence of sweat, which suggests dehydration.
Naked yoga. While doing yoga au naturel may not offer unique physical health benefits, practitioners say it's good for the soul. Aside from the liberated thrill of baring it all, it's considered a way to work toward accepting your own body. Naked yoga is not a sexual experience. At the studio Naked Yoga NYC, for example, removing clothing is a ceremonial process that happens at the start of each class, and nudity—contained to one room—is not permitted in any other part of the building. Proper hygiene is required; participants must come freshly showered.
Laughter yoga. Those who believe that laughter is the best medicine may want to give this a try: Laughter yoga blends attempts to provoke laughter via eye contact and childlike playfulness with breathing exercises. "The idea is that if you're laughing on the outside—even if, initially, you're faking it—it will create an effect on the inside that brings joy and releases endorphins," says Mary-Laurence Bevington, director of Movement Climbing & Fitness in Boulder, Colo. Indeed, research suggests that laughing generates feel-good hormones while lowering levels of the stress hormone cortisol, and that it boosts the immune system, improves blood flow, and increases oxygen intake, which replenishes and invigorates the body's cells. Laughter yoga has been introduced into senior centers, cancer wards, corporations, and prisons.
Koga. This kickboxing-yoga hybrid works every muscle in the body. Koga involves kicking, throwing punches, assuming fighting stances, and bending into yoga positions. At the end of each set, participants do a yoga pose that coincides with the muscle group they just worked, enhancing the effect. Expect to burn between 800 and 1,200 calories per each one-hour class, according to Koga's creator, Jon Koga. Koga is making its way into school PE programs, and some classes cater to the 65 and older set, who perform movements while seated in chairs.