The most popular and accessible form of yoga does not burn sufficient calories to qualify as an aerobic workout, although it does yield other significant benefits, a new study shows. The eight-week study, commissioned by the American Council on Exercise (ACE), examined hatha yoga in 34 previously sedentary women.
Some of the women participated in three 55-minute hatha classes a week; the others were barred from any form of intentional exercise. The yoga group showed improvements in strength, endurance, balance and flexibility but burned only 144 calories in a session, similar to the energy consumption of a slow walk.
ACE said in a statement that its study was the first to examine the aerobic potential of hatha yoga. Research published last summer linked regular yoga practice with successful weight control, but those findings were based on subjects' self-reported behavior -- a notoriously unreliable method -- and did not consider whether respondents engaged in other exercise. (See The Moving Crew, Aug. 16.)
The lead author of the ACE study, John Porcari, noted that burning calories is "not what [hatha yoga] was intended to do. It is designed to increase strength, flexibility and balance -- and it did all of that" in the study. Porcari, an exercise and sports science professor at the University of Wisconsin, La Crosse, said he is preparing to submit the research for publication in a peer-reviewed journal.
The women in the yoga group showed an overall flexibility improvement of 13 percent compared with pre-study measurements, with significant gains in shoulder and trunk flexibility. They also gained strength, reeling off an average of six more push-ups and 14 more curl-ups at the end of the study than at the beginning. The yoga group also increased one-legged stand time by 17 seconds, on average.
Each yoga class began with five minutes of relaxation and yoga breathing (pranayama), followed by 10 minutes of warm-up exercises (including sun salutations) 35 minutes of yoga postures (asanas) and five minutes of relaxation in the corpse pose (savasana).
John Schumacher, founder and director of Unity Woods Yoga Center in Bethesda, contends that hatha yoga can provide an adequate aerobic workout, though not for beginners.
"The key questions," he said, "are: What postures did they do? How fast? How long did they hold them? How did they link them together?" Hatha beginners cannot expect significant aerobic benefit, Schumacher said, because it takes time to learn how to do the poses correctly before increasing intensity. In fact, Porcari led a companion study of 15 people that showed that power yoga, in which participants move rapidly through hatha poses, burned about 237 calories in 50 minutes and boosted heart rates to 62 percent of maximum on average -- a light aerobic workout.
But, Porcari cautions, the more aerobic the yoga practice, the less benefit practitioners derive in flexibility and relaxation. "By moving quickly through the poses, you will not get the same [muscle and tissue] stretch as you would in slower poses.
"People's expected benefits need to be in line with reality," Porcari said. "People often try to make yoga into this all-encompassing thing. Americans have . . . tried to morph [yoga] into programs that will hit every aspect of fitness, but it was never designed that way." For complete fitness, combine yoga with regular cardio.
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