SAN DIEGO, CA — Today more than 11 million Americans pack fitness studios around the country seeking the mind-body benefits of yoga, but yoga isn't offering them a good calorie-burning workout, according to a study by the American Council on Exercise (ACE).

ACE examined the aerobic benefits and calorie expenditure of Hatha yoga, the most beginner-friendly and widespread practice, and found that although yoga improves strength, endurance, balance and flexibility, it doesn't provide the best calorie burn.

The study involved 34 healthy but sedentary women. Subjects were divided into two groups: a yoga group and a non-yoga group. The yoga group participated in yoga classes three times a week while the non-yoga group was barred from any exercise.

While the yoga group showed numerous improvements in strength (could do six more push-ups and 14 more curl-ups), endurance, balance (had a 17-second increase in one-legged stand time) and flexibility (increased 13 percent), they did not burn significant calories. In fact, one 50-minute session of Hatha yoga burns just 144 calories, similar to a slow walk.

“Yoga is designed to relax the body and help improve musculoskeletal fitness. If you attempt to incorporate calorie-burning elements in a yoga session you may compromise the essential purpose and beneficial effects of the practice,” said Dr. Cedric X. Bryant, chief exercise physiologist for ACE. “Yoga is still a valuable addition to any exercise routine offering the essential elements of flexibility, balance and relaxation; factors often neglected in traditional workouts.”