Do you rely on yoga to meet your 150 minutes of moderate physical activity in a week? You might actually be falling short of your goal, suggests a new review of studies on the physical benefits of the popular mind-body practice. That’s because not all forms of yoga are intense enough to count as moderate exercise, although, depending on how you practice, certain styles certainly can be. It’s estimated that as many as 20.4 million Americans practice yoga. With its increasing popularity, says study author Enette Larson-Meyer, PhD, it’s important for students and health professionals to understand exactly what type and how intense of a workout it really provides. Larson-Meyer is an associate professor at the University of Wyoming, and a certified yoga instructor. Her new research looks at 13 previously published studies on Hatha yoga and several of its variations. Hatha is an umbrella term that describes a practice that integrates physical postures, breathing, and meditative elements; popular Western styles such as Vinyasa, Ashtanga, and Bikram can all be considered branches of Hatha yoga. The review, published in the journal Medicine and Science in Sports and Exercise, found a wide range of metabolic equivalent (MET) values for yoga practices and poses between the 13 studies. MET values are a measure of how hard the body is working, and can be used to calculate calorie burn. According to American College of Sports Medicine (ACSM) guidelines, an exercise with a MET value less than three is considered light intensity. Moderate intensity is between 3 and 6, while vigorous is six METs and up. In the studies included in Larson-Meyer’s review, MET values for full yoga sessions ranged from 2.0 to 7.4 – suggesting that yoga can vary from very relaxed to quite vigorous. The lowest value came from a study evaluating a Nintendo Wii Fit yoga practice, while the highest value came from a group of experienced practitioners flowing quickly through four rounds of Sun Salutations, a series of 12 poses that’s practiced in many modern yoga classes. The review found that most individual yoga postures, when evaluated on their own, had MET values in the light-intensity category. The few that did reach moderate levels included Dandayamana-Janushirasana, Dandayamana-Dhanurasana, Trikanasana, and Tuladandasana. Inversions, such as Sirsasana only received MET values up to 2.5-although the studies did not measure some of yoga’s most difficult poses, such as Crow or Hand Stand. Interestingly, the one study that looked at Bikram yoga did not find significantly higher energy expenditure than those found in studies of other yoga types. Bikram classes follow a set series of poses and are held in 105-degree rooms, and they’re often touted as major calorie burners because of how much participants sweat. But the MET values of Bikram were within the same range as yoga practiced at room temperature, Larson-Meyer wrote. Bikram does not incorporate Sun Salutations or flowing transitions from move to move, she points out, so it may require less energy than other styles. “I know a lot of people who attend hot yoga and they feel like they get a better workout, and that’s great,” says Larson-Meyer. But for people who might be uncomfortable in the heat, it’s good to know that’s not necessarily true – you can get a similar workout in a room at normal temperature. The bottom line, says Larson-Meyer, is that yoga can be whatever you want it to be: a relaxing, light-intensity stretch session or a full-on workout with plenty of high-intensity moments. Choosing a restorative class with more seated poses will likely give you the former, while one that incorporates lots of fast-paced transitions can give you the latter. Sessions that include standing poses and Sun Salutations are also likely to give you a greater burn. Most studies show that yoga is pretty comparable to walking, says Larson-Meyer. But if you really did want to get a higher MET value, it’s still possible by doing some specific harder poses at a faster pace than you normally would.