The Science of Yoga

flow of invisible gases was a different story. That kind of information was hard enough to get with athletes working out on treadmills. The investigators had to fit their subjects with clumsy face masks and tubes that delivered the gaseous flows to measuring devices. But with yoga—given its range of motions and its series of rather profound rearrangements of the human body—the challenge was far greater. Even so, a number of scientific teams made headway over the years.
    Cooper, the VO 2 max popularizer, did no direct investigations of yoga but carefully examined several activities that were similar, including isometrics and calisthenics. His verdict? They did little or nothing to strengthen the heart and raise oxygen consumption.
    “Is your chest heaving?” he asked of the person doing the muscular tensing of isometrics. “Is your heart pounding? Is the blood racing around your system trying to deliver more and more oxygen? Nonsense. None of these beneficial things is going on, nothing that anyone can measure, anyway. We tried it and failed.”
    Yoga’s social rise in the 1970s and 1980s led scientists to start assessing how it measured up against aerobic sports. As fate would have it, one of the first investigations was also one of the best. It was done by scientists at the Duke University Medical Center, in Chapel Hill, North Carolina, a top institution for biomedical research. The team studied nearly one hundred older adults—forty-eight men and forty-nine women. A third did Hatha yoga, a third exercised on stationary bicycles, and a third did nothing out of the ordinary.
    The team’s use of experimental controls set the study apart from what specialists consider an underworld of shoddy research. Controls let scientists zero in on a single variable and avoid subtle misunderstandings. They try to eliminate the complexities of nature and human interaction to ensure that anyobserved changes are the result of the examined factor rather than some extraneous influence. With the Duke study, for instance, the experimental controls let the scientists make sure that the process of simply gathering the subjects to the site of the investigation played no role in the results. What if some walked there? What if some bicycled? What if some ran? Would that affect the fitness measurements? The changes observed in a control group could alert scientists to the existence of an unintended influence and help them eliminate it from their findings. The big challenge for a scientist designing a study with human subjects is to make the experiences of the experimental and control groups as similar as possible—with the exception of the issue under examination. Without such precautions, researchers have no way of knowing whether the changes observed in an experiment would have happened anyway. The practical difficulty of such precautions is their added expense. The recruitment of more subjects—and their subdivision into different kinds of activities—can result in the need for more money, more personnel, more data analysis, and more administrative burdens. But the scientific benefits are usually seen as worth the costs.
    In the Duke study, the hundred or so subjects, including the control group, did their designated activities for a total of four months. To get around the measurement dilemma, the team made no readings during the months of assigned activities and instead opted for detailed assessments before and after the training.
    The results, published in 1989, were unambiguous. The aerobics group improved its VO 2 max significantly, raising peak oxygen consumption by 12 percent. But the yogis showed no increase whatsoever and in fact registered a bit of a decline, though it was judged to be statistically insignificant.

    A surprise also emerged.The scientists were intrigued to discover that the yogis, despite their poor showing in terms of aerobic conditioning, nonetheless felt better about themselves. The subjects reported enhanced sleep, energy, health, endurance, and flexibility. They described how they experienced a wide range of social benefits, including better sex lives, social lives, and family relationships. Psychologically, the scientists said, the yogis reported a number of improvements. They had better moods, self-confidence, and life satisfaction. With few exceptions, they said they looked better.
    The Duke findings hinted at a fascinating split. It was one thing to do good for the hidden intricacies of human