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 VO2 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 any observed 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 VO2 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 physiology and quite another for an individual to feel good about themselves. It was the difference between improved fitness and outlook. The subjects who did yoga felt they had received a wealth of benefits even though the Duke scientists found no indication whatsoever of aerobic gains. Their discussion of the research findings hinted at their fascination. The improvements in attitude, the scientists said, “are worth noting.”
The Duke team—unknowingly—had stumbled on one of yoga’s secrets. The next chapter will explore the science of how the discipline lifts the human spirit.
Yoga fared slightly better in subsequent studies of aerobic conditioning. One reason was a subtle change in the discipline that put growing emphasis on energetic poses and styles. The new forms downplayed stationary postures for ones that required a much greater level of movement and physical activity, creating a more athletic experience and increasing the aerobic challenge.
Sun Salutation, Surya Namaskar
To a surprising degree, the new vigor centered on a single activity— Surya Namaskar, Sanskrit for “salutation to the sun.” Today it is one of yoga’s most popular poses. The student, rather than remaining motionless in a fixed posture, moves through a fluid series of up to a dozen interconnected poses that go from standing to bending to lying prone to standing back up and to stretching backward. If done rapidly—and repeatedly—the sequence can leave the heart pounding and the lungs gasping for air. It therefore has elements of a cardiovascular workout.
The Sun Salutation and its relatives are, by nature, quite malleable. They can be sped up or slowed down to suit individual preferences. In their adaptability, they are quite different from yoga’s static postures. The situation is similar to what we experience in terms of gait. When standing motionless, we are, by definition, stationary. But once in motion, we can move forward in a number of ways: walking, jogging, running, or racing ahead as fast as we can. It depends on what we want to do.
The Sun Salutation appears to be fairly recent in origin. The Encyclopedia of Traditional Asanas—published in India by the Lonavla Yoga Institute, founded near Gune’s ashram by one of his students—draws on nearly two hundred books and unpublished manuscripts to describe many centuries of pose development but says nothing about the Sun Salutation. So, too, the asana makes no appearance in the how-to guides of Gune (1931), Sivananda (1939), and other early teachers.
The pose most likely arose in the early twentieth century as the Mysore palace and Krishnamacharya mixed traditions of British gymnastics and native wrestling. Whatever its exact origins, the Sun Salutation debuted as an important new feature of Hatha yoga in the
1930s, spreading slowly through India and the world. The idea behind the pose and kindred postures was what Krishnamacharya called Vinyasa (vi denotes “in a special way” and nyasa “to place”). It stood for the flowing movements that he developed to join the individual poses into a new kind of graceful activity. The result was a kind of yoga ballet.
In the West, students of yoga learned about the pose in a number of ways. Krishnamacharya’s student Sri K. Pattabhi Jois played an important role in popularizing the series of movements and the Vinyasa system, calling it Ashtanga (or eight-limb) yoga, after the sutras of Patanjali and their eight rules. Starting in the late 1960s, Westerners began traveling to Mysore to study yoga with Jois. Slowly Ashtanga grew in popularity, especially among the physically ambitious in the West who were seeking yoga’s most athletic expressions. The aggressive style required skill and power, and could leave a student bathed in sweat.
Science looked into Ashtanga as the style gained in popularity and found that, compared to traditional yoga, it posed a greater challenge to the heart. One study examined sixteen volunteers. The human heart beats about seventy times per minute. On average, the hearts of the yogis quickened to ninety-five beats while doing Ashtanga, compared to eighty beats during conventional Hatha. The Ashtanga factor represented a rise of roughly 20 percent.
The more difficult question was whether the increased thumping of the heart that resulted from faster poses and faster styles translated into measurable improvements in cardiovascular fitness. That soon became the question.
Ezra A. Amsterdam was hitting new highs in his career when yoga caught his eye. A senior cardiologist at the medical school of the University of California at Davis, he had devoted himself to the study, practice, and teaching of ways to prevent heart disease, the nation’s number one killer. He was prolific. His résumé boasted hundreds of articles. Recently, he had even founded a journal—Preventive Cardiology—the first of its kind, published by John Wiley & Sons, a respected firm. Amsterdam’s own studies ranged from investigations of diet and exercise to drugs and therapy as ways to promote a healthy heart and fend off cardiovascular disease. He lived in sunny California and practiced what he preached, maintaining a trim figure into his sixties.
Yoga as a field of scientific inquiry seemed wide open to Amsterdam, his interest stimulated by what he saw as “the lack of objective study.” Growing numbers of people were practicing yoga, and doing so in new, innovative ways that were often quite vigorous. A fresh look at the relationship between yoga and aerobics seemed to beckon.
Another factor was his daughter. Dina suffered from an eating disorder and was twenty-five pounds overweight when she starting doing yoga. It worked like a charm. The discipline helped her shed weight, feel good about herself, and get in excellent shape. She studied with Rodney Yee, a yoga star, taking his advanced teacher training course. Dina became a devotee of the discipline and proceeded to teach classes in the San Francisco area. She had a big smile and a reputation for rigor, sensitivity, and infectious enthusiasm. Dina—a graduate student at Stanford University—also had a deep interest in the science of yoga and wellness. She had “many lively discussions” with her father, she recalled, and was delighted when he decided to do a yoga study.
Amsterdam was determined to give yoga a serious look. Was the discipline all that it was cracked up to be? Was it, in fact, all that Dina needed to stay fit, to maintain a healthy heart? Could any practitioner reap the benefits? If so, yoga might join the elite club of rigorous sports and activities that public health authorities had singled out as highly beneficial—especially in preventing heart disease and the kind of cardiovascular illnesses that Amsterdam knew only too well.
He worked with a team of specialists from the University of California at Davis, a good school in a highly respected system. Except for him, the three researchers came from the department of exercise science, anchoring the study in a solid analytic tradition. In terms of capabilities and intellectual depth, the team appeared to be quite strong.
But the investigation, begun on an auspicious note, soon encountered a number of difficulties. The biggest was the lack of major financial support for the study, which forced the scientists to limit its size and design. They lined up just ten volunteers—one man and nine women. Compared to the Duke study, that was one-tenth the number of subjects. Moreover, their examination had no control group. The low numbers and the absence of controls increased the possibility that any observed changes might result from random variability rather than yoga. A final limitation was that the students were required to do a minimum of just two workouts a week for two months—a fairly short time in which to see the physiological effects of yoga. By contrast, the Duke study had proceeded twice as long.
Even so, the yoga session itself was fairly intense, lasting nearly an hour and a half. It included ten minutes of breathing exercises (pranayamas), fifteen minutes of warm-up exercises, fifty minutes of yoga postures (asanas), and ten minutes of relaxation in the Corpse pose (Savasana). A centerpiece was the Sun Salutation. The students did two or three cycles of its fluid movements, stretching and bending back and forth. In addition, the workout featured a number of other vigorous moves that went beyond yoga’s tradition of stationary poses. They included lunging forward on the legs and bobbing up and down in what the investigators called the Frog.
Different schools of yoga mean different things when they talk about the posture. The energetic pose adopted by the Davis team was a newcomer to yoga, its origins unclear. No classic text mentions its repetitious movements. It starts with students squatting down, putting their hands on the floor, and then straightening out their legs. While raising their bottoms high in the air, they keep their heads as close as possible to their knees. The movement ends with the students lowering themselves back down into the squat. Modern texts that describe that style of Frog recommend doing it anywhere from fifteen to more than one hundred times, its rhythms growing increasingly fluid and fast as the student warms up.
The ten volunteers in the Davis study had led fairly sedentary lives. A condition for participation in the study was that they had engaged in no regular physical activity—including yoga—for the previous half year. Moreover, the researchers had the students refrain from all other forms of exercise. As with the Duke study, the researchers got around the measurement problem by performing the physiological assessments before and after the yoga training.
Having gathered and analyzed the data, the Davis team got ready to present its findings to the world. That meant finding a reputable journal.
Not all public representations of science are created equal. Journals range from bad to great. A minimum requirement for a good journal is that it conducts a process known as peer review—that is, it maintains panels of scientists working in the field who review any proposed article. They exercise what amounts to quality control, making sure a submission hangs together and, if weak, gets rejected or revised to address the inadequacies. Some of the world’s best journals are published by professional associations and have long histories. Science, for instance, was founded in 1880 with the financial support of Thomas Edison and is now published by the American Association for the Advancement of Science, a large professional group headquartered in Washington. The best journals—the ones most widely accepted and admired within the scientific community—achieve good 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 relatio
nship, 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 Science of Yoga: The Risks and the Rewards Page 9