The Science of Yoga

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 studies had significant flaws. For instance, subjects were inexperienced or had been forced to wear clumsy masks and mouthpieces. “Such techniques,” the scientists noted, “may alter the performance of the yoga activities and therefore provide invalid estimates.” Invalid estimates. In the polite world of scientific discourse, that was tantamount to ridicule.
    Seeking better results, the scientists made their measurements while the subjects did yoga in a special chamber that could track overall changes in respiratory activity. It let the yogis move about freely even while being scrutinized intimately. Known as a metabolic chamber, the rare and costly piece of scientific equipment was located at Saint Luke’s–Roosevelt Hospital on the city’s Upper West Side, near the Columbia campus. It was, in effect, an airtight cell. Machines linked to the metabolic chamber could measure a subject’s exact consumption of oxygen, exhalation of carbon dioxide, and radiation of metabolic heat. Columbia scientists often used the chamber to study obesity. They would examine a subject’s metabolic rate during meals, sleep, and light activities. But now they lent their apparatus to the scrutiny of yoga. The aim was not to track the addition of layers of fat but to seehow efficiently yoga burned calories by fanning the body’s metabolic flames. In terms of sophistication and accuracy, the chamber was light-years away from the rough bags that Hill had strapped on his runners, and from the traditional sets of before-and-after measurements that some modern scientists had used to track VO 2 max. It was cutting-edge.
    The architects of the New York inquiry, as with most scientists who study humans, made sure its design included the