The Science of Yoga

better enjoy their lives and leisure time.
    By 1900, investigators had identified a factor that they called vital capacity. It measured a person’s ability to breathe deeply—seemingly a good measure of fitness because breathing is considered a foundation of the metabolism and, in earlier days, was viewed as an expression of the human spirit and soul. Science saw deep breathing as similar to blowing on a fire—in theory it fanned the body’s metabolic flames.
    Seeking precision, scientists defined vital capacity as the maximum volume of air that an individual could exhale after a deep inhalation. A sedentary life was found to reduce vital capacity, and an active life to increase it. Scientists quickly developed a refinement known as the vital index, which sought to eliminate differences due to age, size, sex, and other individual factors. It consisted of the ratio of vital capacity to weight. Early in the twentieth century, athletes aspired to a high vital index as an indication of competitive excellence.
    Gune became an enthusiasticfan of the vital index and cited yoga’s impact on the physiologic measure as evidence of the discipline’s power to raise human vitality. Viewed narrowly, his claims were exactly right. Pranayama gave the lungs, the chest, and the abdominal muscles a comprehensive workout and improved the flexibility of the rib cage. The natural result was an aptitude for deep breathing. The big question was whether the pulmonary skills translated into heightened fitness.
    Gune had no doubts. In his estimation, yoga, with its proven ability to expand the lungs, outshone all other sports and systems of exercise. And he said so bluntly. Shortly after starting his ashram, he declared that the discipline excels at “increasing the vital index” and improving all aspects of life. Yoga, Gune insisted, let students attain the “physiological perfection of the human body”—not improvement or development but perfection. “There can be no other system more suitable.”
    Unfortunately, just as the guru was seizing on the vital index as evidence of yoga’s superiority, scientists in Europe and the United States were abandoning the measure as deceptive and potentially meaningless. For instance, they noted that the vital index of a growing child usually fell steadily between the ages of, say, ten and twenty, since body weight during those years increases faster than lung size. Yet common sense suggested that those same years saw great rises in athletic prowess.
    So the question arose with new urgency: What did, in fact, define the human capacity for physical vigor and, if such a factor existed, could science find a way to measure its development?
    In the 1920s, as Gune was beginning his program of experimentation, some of the world’s best minds took up that question. A star was Archibald V. Hill, an English physiologist who won the Nobel Prize in 1922 for showing how muscles use energy.
    Thirty-seven at the time of the award, Hill wore a proper British mustache and was married to Margaret Neville Keynes, the sister of the economist John Maynard Keynes and a social worker who had written extensively on child labor. The couple had two boys and two girls. Hill, as it turned out, was just starting a long, productive career. After his Nobel work, he turned to the related question of how muscles get their oxygen. It was the flip side of the energy coin—focusing on origins rather than ends. His agenda was quite sensible for an ambitious scientist curious about the fundamentals of biology.
    Hill brought to hisresearch an abiding personal interest in sports and fitness. As a young man, he had run competitively, covering two miles in a little more than ten minutes—a fast pace for the day. As an adult, Hill often ran a mile before breakfast. For his studies of oxygen, Hill and colleagues designed experiments meant to reveal the exact dimensions of its invisible uptake. His main venue was a grassy track. His runners strapped to their backs bags into which they would breathe at set intervals. Later, analysis of the contents revealed the quantity of oxygen consumed.
    Careful measurements showed that the runners—once achieving a certain intensity of effort—could increase their oxygen uptake no more. The situation held steady no matter how much they sped up their pace or how hard they pushed themselves. It was a hidden barrier. Like a bellows blowing air, the heart and lungs turned out to work beautifully at