The Science of Yoga

1970s, jogging became fashionable.
    The surge of activity resulted in a number of scientific inquiries that examined what aerobic exercise could do not only for athletics but health. The results were dramatic. Perhaps most important, the studies showed that aerobic exercise lowered an individual’s risk of heart attack and heart disease— the leading cause of death in the developed world. It also reduced the prevalence of diabetes, stroke, obesity, depression, dementia, osteoporosis, hypertension, gallstones, diverticulitis, and a dozen forms of cancer. Finally, it helped patients cope with all kinds of chronic health problems. Frank Hu, an epidemiologist at the Harvard School of Public Health, praised the benefits as exceptional. For general health, he called vigorous exercise “the single thing that comes close to a magic bullet.”
    Why did it do so much good? Scientists found that forceful exercise improved the performance of virtually every tissue in the human body. For instance, it produced new capillaries in skeletal muscles, the heart, and the brain, increasing the flow of nutrients and the removal of toxins. Scientists also discovered that it raised the number of circulating red blood cells, improving the transport of oxygen. Still another repercussion centered on blood vessels. It caused their walls to produce nitric oxide, a relaxant that increases blood flow.
    The wide health benefits prompted medical groups to call for regular exercise and public institutions to set recommended levels. The American College of Sports Medicine said healthy adults should engage weekly in at least three vigorous exercise sessions, each twenty to sixty minutes long. The American Heart Association called for at least five sessions. Many other groups, including the President’s Council on Physical Fitness, made similar recommendations. The push was global. In Geneva, the World Health Organization said regular aerobic exercise held out the promise of “reducing cardiovascular diseases and overall mortality,” the rate at which people die.
    In short, vigorous exercise for health maintenance and enhancement became a modern credo. The message was etched in stone. Experts might quibble over the amounts.But they agreed on the principle and did whatever they could to promote its public acceptance.
    It took decades for scientists to consider how yoga measured up. Part of the problem was the relatively small size of the yoga community and its limited ability to win scientific attention. Another was the difficulty of monitoring the aerobic status of practicing yogis. It was easy for investigators to study how yoga could increase an individual’s flexibility and muscular strength—fair measures of fitness. But gauging the 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.