If you could spend 90 minutes today doing anything, what would it be? I’d choose shopping, lounging beachside with a cold drink in hand or watching bad (yet so good) reality TV. Was “sitting on the floor in a hot room with a bunch of other sweaty people” on your list? Maybe not, but it’s on someone’s list — maybe your neighbor’s; maybe your office cubemate’s.

Over the past four years, the number of Americans practicing all types of yoga has shot up by nearly 30 percent — totaling up to somewhere around 20 million people. That’s quite a few folks getting in touch with their inner “om.” It makes sense, though, since practicing this ancient form of movement provides a number of healthy benefits, including stress reduction and an improved outlook.

Ultimately, “all yoga is good yoga,” says Sandy Eang, an instructor at Bikram Yoga Grand Central in New York City. But what about the pumped-up forms of yoga that celebs like Jennifer Aniston, Beyoncé and even George Clooney swear by — such as power yoga, hot yoga and Bikram?

“Yoga not only helps with toning, strengthening and lengthening your muscles, but adding a level of heat can give your heart and circulatory system a workout, expanding capillaries and improving circulation,” says Denise Nann, who’s also an instructor at Bikram Yoga Grand Central in New York City. Adding heat might also assist in moving toxins out of the body, she says.

Whether you’re a yoga newbie or are looking to turn up the heat on your current practice, here’s some hot information for you:

Hot: Power Yoga

If you watched Friends when it originally aired, you’re likely familiar with “gym yoga” (now referred to as “power yoga”), a vigorous, fitness-based approach to Vinyasa-style yoga. (If you’ve ever read Lady Gaga’s Twitter updates, you’ll know she’s somewhat smitten.)

Originally modeled on the Ashtanga method, power yoga has evolved to focus on core and upper-body strength and flexibility. Your local gym likely offers a power yoga class that you can integrate into your normal fitness routine. Unlike other types of hot yoga, though, the temperature, session length and series of poses performed in power yoga all depend on the gym and instructor. (You could find yourself in a 60-minute session at 90 degrees F… or a 90-minute class at 105.) While the room may not be as warm as it is with other hot yogas, there’s no doubt that power yoga’s faster, fitness-based approach will have you nice and moist by the end of the session. Wear comfy clothes that allow for movement, and plan on doing some core-strengthening poses that will make your muscles beg for mercy during the class (but feel kind of incredible afterward).

Hotter: Hot Yoga

If you want a warmer environment and more traditional moves, gear up for hot yoga, which is Vinyasa-style yoga performed in a room that’s usually heated to 95 or 100 degrees F. Hot yoga is like yoga’s middle child: Unlike power yoga, it guarantees heat; unlike Bikram — which is discussed below — class length, temperature and the number of poses vary from studio to studio.

Sign up for hot yoga with no expectations, and make a commitment to yourself to do it at least three times. Since you’ll sweat profusely in places you didn’t even know it was possible to sweat, it’s safe to say that your first session may be uncomfortable. However, instructors say that this discomfort lessens with time and experience. To ease the initial shock, Eang and Nann recommend that you wear clothing that allows you to move easily, and that you avoid eating anything in the three hours leading up to class. “It’s best to come in on an empty stomach,” says Nann, “but be sure to hydrate well a few hours beforehand, to prepare for the hot environment.” 

Hottest: Bikram

For the guaranteed hottest yoga session in town, opt for Bikram. Each 90-minute yoga class consists of a set sequence of 26 postures (hatha series) designed to work every part of your body, including your muscles, joints, glands and organs. It also warms and stretches muscles, ligaments and tendons. Oh, and did we mention that the room is heated to 105 degrees?

While Bikram is the hottest of the hot yogas, it is also the most uniform. “Something like the triangle pose has many different versions,” says Nann. “With Bikram, the moves will start to feel familiar across disciplines.” As 105 degrees is the most ass-kicking yoga temperature, follow the same tips for eating and staying hydrated as you would for hot yoga. Also, Nann recommends wearing shorts and a tank top, which “exposes your muscles and allows you to see how you’re working them during each session.”