Today more than 11 million Americans pack fitness studios around the country seeking the mind-body benefits of yoga, including increased flexibility, strength, balance and muscle tone. But is yoga also a good calorie-burning workout? In an exclusive study, the American Council on Exercise (ACE), America's nonprofit fitness advocate, examined the aerobic benefits and calorie expenditure of Hatha yoga, the most beginner-friendly and widespread practice.

Lead researchers Dawn Boehde and John Porcari, Ph.D., FACSM, from the University of Wisconsin-La Crosse recruited 34 healthy but sedentary women (average age of 33) for the study. Before beginning the study, participants were given the same series of tests evaluating their flexibility, balance, aerobic fitness level and muscular strength and endurance.

The subjects where divided into two groups: a yoga group and a non-yoga control group. The yoga group participated in 55-minute Hatha yoga classes three times a week during the eight-week study period while the non-yoga group was barred from any form of exercise.

The study concluded that while the yoga group showed numerous improvements in strength and endurance as well as improved balance and flexibility, they did not burn a significant amount of 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. “While the ACE study shows that a Hatha yoga session burns a relatively small amount of calories, 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.”

Yoga group participants did show the following improvements:

-- Yoga participants' total body flexibility improved by 13 percent, with significant results in shoulder and trunk flexibility

-- Muscular fitness also improved in the yoga group enabling them to do an average of six more push-ups and 14 more curl-ups

-- Yoga participants experienced a 17-second increase in their one-legged stand time

Complete study results appear in the September/October 2005 edition of ACE Fitness Matters magazine or on our Web site at acefitness.org/getfit/yoga.aspx.