The Science of Yoga

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 imposition of controls meant to increase the likelihood that any observed changes were real rather than false clues or statistical flukes. Thus, the subjects in the metabolic chamber engaged sequentially in three different activities—reading a book, doing yoga, and walking on a treadmill. To provide a more detailed basis for comparison, the scientists had the subjects walk on the treadmill at different speeds. The imposed rates were two miles per hour and three miles per hour, the latter a fairly vigorous pace.
    The yoga was pure Ashtanga, the brisk, fluid style descended from Krishnamacharya. The workout began with twenty-eight minutes of Sun Salutations followed by some twenty minutes of standing poses such as the Triangle and Padahastasana, a forward bend in which the student grabs the feet and brings the head down to the knees. It ended with eight minutes of relaxation in the Lotus position and the Corpse pose. Overall, the yoga session lasted nearly an hour. Its strong focus on Sun Salutations made the routine one of the most vigorous to undergo careful examination.

    Hands to Feet, Padahastasana
    Despite the added zing,the scientists concluded that the yoga session failed to meet the minimal aerobic recommendations of the world’s health bodies. Its oxygen demands, they reported, “represent low levels of physical activity” similar to walking on the treadmill at a slow pace or taking a leisurely stroll.
    The only glimmer of cardiovascular hope centered, once again, on Sun Salutations. The New Yorkers found the oxygen challenge of the pose “significantly higher” than for the slow treadmill. A practice incorporating Sun Salutations for at least ten minutes, they wrote, may “improve cardio-respiratory fitness in unfit or sedentary individuals.” But the flip side, the scientists added, was that the posture offered few heart benefits for seasoned practitioners.
    Seeking a wide context, the scientists were careful to note that other research had demonstrated that yoga aided the body and mind in ways that extended far beyond athletics and aerobics. Hagins, the lead researcher, remarked in a university news release that the discipline had “positive health benefits on blood pressure, osteoporosis, stress and depression.” Yoga, he added, “may convey its primary benefits in ways unrelated to metabolic expenditure and increased heart rate.”
    That kind of prudence became the standard view in the world of science. Decades of uncertainty ended as a consensus emerged that yoga did much for the body and mind but little or nothing for aerobic conditioning. The California study receded as an anomaly, and the investigations in Texas, Wisconsin, and New York got cited repeatedly and respectfully