The Science of Yoga

meant to increase yoga’s vigor. Porcari said that adding more energetic postures as a way to boost cardio benefits would, by definition, come at the expense of flexibility, balance, and the other traditional benefits.
    “It’s always a trade-off,” he said. “Yoga was designed for relaxation, primarily. The more aerobic you make yoga, the less improvement you’ll see in those other areas.”
    Many yoga studies go unnoticed. The Wisconsin inquiry made waves, probably because its sponsor was the American Council on Exercise, a nonprofit group that seeks to protect consumers from risky and ineffective fitness programs. That gave the study added authority and exposure. The council, based in San Diego, published a digest of the Wisconsin study in its magazine and sent out a press release. The statement noted that the Wisconsin scientistshad found that each Hatha session burned just 144 calories—similar to a slow walk.
    “Aerobics?” The Washington Post asked in its headline. “Not Among Yoga’s Strengths.”
    Yoga Journal took notice—defensively, acting like a true believer in denial. Its headline said it all: “Flexible and Fit.”
    The magazine faulted the Wisconsin study, as well as the reaction of the news media, and went on to cite new evidence of yoga’s aerobic benefits. Once again, it found support at the University of California at Davis—the main source of its original good news on VO 2 max some four years earlier. A Davis researcher, Yoga Journal reported, had studied four yoga instructors who displayed levels of fitness comparable to someone who jogged three or four times a week. The news media, the article insisted, had fallen for a misleading story and had missed an inspiring one.
    But the new evidence was thin. Yoga Journal gave no details about the new Davis study, just the claims. And, as it turns out, the study was never published. Its existence amounted to a rumor, although the readers of Yoga Journal could be forgiven for thinking otherwise.
    The more obvious problem was that the Davis scientist had drawn a comparison between extensive and small efforts—comparing teachers who did “several hours of yoga a day” to joggers who ran as little as three times a week. The finding implied that running was far more aerobic—just what an impartial observer might conclude.
    “I think you just proved the point,” a reader wrote Yoga Journal in noting the lopsided comparison.
    A final study, published in 2007, sought to settle the debate once and for all. It fairly breathed thoroughness and rigor. For instance, it did its recruiting in the studios of Manhattan, where youth, fierce competition, and starry clientele had resulted in challenging routines and gifted students—some of the best the planet had to offer. The sites ranged from downtown, to Midtown, to the Upper West Side. They included the torture chambers of Bikram Yoga (“we forge bodies and minds of steel”), the stylish removes of Levitate Yoga (“be free to wear the latest Louis Vuitton or Prada items”), and the sunny halls of the World Yoga Center (“created with a pioneering and idealistic spirit”).
    The researchers came from the Brooklyn campus of Long Island University as well asthe Mailman School of Public Health of Columbia University, a star of the biological sciences. They knew their stuff. The lead scientist, Marshall Hagins, had a doctorate in biomechanics and ergonomics and a clinical doctorate in physical therapy, and had practiced yoga for a decade.
    The study’s funding signaled its gravitas. Often, yoga investigators list no source of financial backing in their published work, implying that they undertook it on their own or with the aid of anonymous colleagues. That was the case with the Davis study. Such research tends to be modest in scope because the funding tends to be modest. Not so mainstream science. There, investigators typically go out of their way to thank their patrons—in the life sciences, often federal agencies. So it was with the New York study. The team in its published report said it had received support from the National Institutes of Health, the world’s premier organization for health-care research.
    The New York team recruited twenty subjects who had practiced yoga for at least one year, felt comfortable doing Sun Salutations, and could perform such advanced poses as the Headstand. The group consisted of two men and eighteen women.
    The scientists judged that some of the previous