With dozens of sexy celebrities touting its arm- and ab-sculpting powers and stress-reducing abilities, it’s no surprise that yoga has had a major surge in popularity. Sure, yoga has been around for thousands of years, but in the US it has never been as hot as it is today.

Yoga classes are offered everywhere from traditional studios to health clubs to community centers. Unfortunately, “there’s more demand for yoga than there are qualified teachers,” says Barbara Benagh, a nationally recognized yoga teacher and director of the Yoga Studio in Boston.

Just because a facility offers a yoga class doesn’t mean the class is appropriate for the public. Students should be aware of the potential hazards of yoga, and carefully assess whether a yoga situation is right for them.

Trusting Your Teacher

“Almost anyone can get a ‘weekend certificate’ to teach yoga,” says Mara Carrico, a San Diego-based yoga instructor, author of Yoga Journal’s Yoga Basics, and spokesperson for the American Council on Exercise. “That’s just not enough.”

“Do you want to be taking yoga from someone who’s been doing it for a weekend longer than you?” Benagh asks. “Many people who’ve never practiced yoga try to get into teacher training.”

While various forms of yoga have different training requirements, Carrico believes teachers should have at least 200 hours of training, the minimum recommended by the Yoga Alliance, an alliance of yoga organizations and instructors seeking to create national teaching standards.

Don’t be afraid to ask yoga instructors about their training, how long they’ve been teaching, and how long they’ve been practicing. You should also ask the studio or health club about their teacher requirements and screening methods. Unqualified teachers may increase your risk for doing a posture incorrectly, pushing beyond your abilities, or performing poses inappropriate for your health and fitness level.

Regardless of how long they’ve trained, avoid teachers who don’t pay attention to you.

“Some yoga teachers are more concerned with their own workout than with your safety,” says Carrico.

Safety First

Yoga classes come in many forms and many levels. Start with a beginner class instead of rushing into advanced power yoga. Shop around for the class that’s right for you.

Once in class, the standard mantra holds true: listen to your own body and do what feels right.

“Muscle exertion is a good thing—keep going,” says Jolie Bookspan, PhD, a sports medicine specialist and yoga instructor. “But if you feel any joint pain, stop.” Be especially careful with postures that involve the knees, neck, lower back, and shoulders. “These are vulnerable joints—they’re easy to strain,” Benagh says.

All students should be cautious and pay attention to any joint pain, but if you’ve had any injuries, surgery, or a history of pain, let your instructor know. A good instructor should ask students about joint problems and suggest alternative postures if necessary. Proper alignment is key to protecting your joints in many postures. Allow your instructor to adjust you, and if something feels wrong—ask for help.

And if you’re pregnant, have hypertension , a heart condition, or any other pertinent medical history, inform your instructor at the beginning of class and ask if you should take any precautions.

“Ultimately, you’re responsible for yourself,” warns Benagh. “Not even the most qualified teacher can guarantee that nothing will happen to you.”

The Hot Zone

Many yoga classes are conducted in rooms heated to 100 degrees or more. Hot yoga can be a wonderful, sweaty, challenging experience. But it can also pose risks beyond those of regular yoga.

Pregnant women and people with hypertension or heart disease should avoid hot yoga—it’s too intense. But even if you’re perfectly healthy (and not pregnant), be wary. You get so warm in a heated room that you can have what Benagh calls a “false sense of flexibility.” This can lead to muscle injury if you push yourself too far. And you’ll be sweating quite a bit, so drink plenty of water before and after class to avoid dehydration.

Make sure that the room in which you practice is clean and well-kept.

“So much heat and sweat in a room that’s not well ventilated can create a breeding ground for bacteria,” Benagh says. Carrico adds that the air ducts should be cleaned frequently, as should the carpet or floor.

Even in non-heated rooms, shared mats—especially those that aren’t cleaned and replaced regularly—could have festering bacteria. Consider purchasing a mat of your own. Or “bring a towel if you’re worried about cleanliness,” advises Dr. Bookspan.

As with your physical safety, though, the cleanliness of the studio where you practice is ultimately up to you. So if yours feels filthy, find someplace new.

Yoga provides a great workout, as well as a means for relaxation. It also offers therapeutic value for many disorders. It's a good workout for most everyone, just be sure you take the necessary precautions before heading into lotus.