The Science of Yoga

best journals—the ones most widely accepted and admired within the scientific community—achievegood names by virtue of long histories of responsible reporting, quality articles, and exhaustive peer review.
    In 2001, the Davis team laid its findings before the world. It did so not in a sports journal, not in a physiology journal, and not in a general-interest journal of good reputation, such as Science. Instead, it reported the yoga findings in Preventive Cardiology , the journal that Amsterdam had recently founded and on which he served as editor in chief.
    In theory, his editorial control did nothing to diminish the study’s credibility. The journal, after all, was peer reviewed. Amsterdam told me that the manuscript was sent to several reviewers with whom he had no relationship, making their evaluation “blind” and unbiased. Moreover, Preventive Cardiology was the official journal of the American Society for Preventive Cardiology, a professional group. Still, a situation in which the most important gatekeeper at a journal also submits his or her own work for publication can foster a perception of a conflict of interest. Did reviewers go easy on the manuscript to curry favor? Did the editor have a financial stake in the journal’s success, and thus an incentive to make bold claims that would draw wide attention, raising the journal’s readership?
    A related problem centered on the sheer magnitude of Amsterdam’s submissions. Preventive Cardiology carried so much of his own work that the journal, despite its professional affiliation, seemed less like an impartial forum than a vanity press. The same issue that featured the yoga study carried another one of his papers. In all, the quarterly journal that year published four of his articles. No other author came close. His work, except for the yoga study, focused on medical aspects of heart disease.
    That led to a final topic of procedural significance—whether Preventive Cardiology was the right place for the yoga study. The Davis team reported a range of athletic findings, not just ones related to the heart. It seems like its natural home would have been an athletic forum, perhaps the Journal of Exercise Physiology. But the authors, for whatever reason or reasons, instead chose the pages of Preventive Cardiology .
    The study came across as strong and authoritative. For instance, the Davis scientists reported that the fledgling yogis racked up solid gains in muscular strength. One test centered on knee extension—the act of straightening out the leg while raising a heavy weight. On average, the students improved 28 percent.They also showed greater flexibility. On average, they increased the amount they could bend forward (as in the Frog) by 14 percent. Their backward stretches (as in the Sun Salutation) improved even more, rising on average nearly 200 percent.
    Unfortunately, the gains in aerobic conditioning—the primary interest of Amsterdam the cardiologist—were quite small. Even so, the Davis scientists judged them to be statistically significant. They reported that VO 2 max rose on average 7 percent. Moreover, they judged that the positive finding stood out from all previous studies, marking a milestone in the scientific evaluation of yoga.
    “The present study,” the authors declared, “is the first to show improvements in cardiorespiratory endurance by direct measurements.” The scientists concluded that the overall results of their study indicated that Hatha yoga “would meet the objectives of current recommendations to improve physical fitness and health.”
    That was a big claim for what was indisputably a small investigation—for what its authors conceded was a “pilot study” that amounted to a preliminary look in search of noteworthy trends. The scientists offered no comment on how the small observed gain in aerobic conditioning measured up to the official recommendations of such groups as the American College of Sports Medicine, although their use of the conditional tense, “would meet,” bespoke caution.
    Nor did the authors put the aerobic figure into a wider context. They made no comparison of the 7 percent rise to what a sedentary individual might gain from endurance training, where scientists had found that peak oxygenation could increase up to 50 percent.
    “In summary,” the Davis scientists said, “the results of this investigation indicate that eight weeks of Hatha yoga practice can significantly improve multiple