The Science of Yoga

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 fanning the body’s inner fire but had intrinsic limits that no level of effort could overcome.
    In pioneering reports of 1923 and 1924, Hill and his colleagues coined the term “maximal oxygen uptake,” defining it as the peak consumption of oxygen during exercise that got incrementally harder. It soon became the gold standard of physical fitness and exercise physiology—the single most important factor in determining what made for athletic excellence. The vital index, meanwhile, was cast onto the scrap heap of history.
    What determined the maximum uptake? Amazingly, peak oxygenation of the body was found to have little or nothing to do with lung size, lung elasticity, the depth of breathing, eating habits, vitamins, the amount of sleep, good posture, body weight, or whether an individual possessed an unusually potent form of hemoglobin or some other energizing factor in the bloodstream. No. The scientists concluded that it rested on one main factor—the size of an individual’s heart and its ability to send blood rushing through the lungs and blood vessels to the muscles. In short, the secret of athletes who drove themselves to heights of physical performance centered on a big heart.
    A central myth of Hatha yoga—one Gune had identified—held that deep breathing increased the blood’s oxygenation despite the relative stillness of the body and the modest use of the muscles during yogic practice. Hill ignored that misunderstanding. His discovery centered on the quantity of blood oxygenation rather than mythic attributes of quality. It bespoke huge volumes of rushing blood. Peak oxygen consumption was typically expressed inliters of oxygen—with top athletes each minute drawing in six, seven, or even eight liters—in other words, up to two gallons. Two gallons. It was a flood compared to a phantom trickle. With great elegance, Hill and his colleagues overturned the misconceptions of the vital index to show that the central element of peak oxygenation rested on the workings of the heart rather than the lungs.
    Today in sports medicine and exercise physiology, peak oxygen consumption is known by the ubiquitous acronym VO 2 max. In the argot of science, the V stands for volume, the O 2 for oxygen in its usual chemical notation, and “max” for maximum. VO 2 max is accepted around the globe as the best single measure of cardiovascular fitness and aerobic power.
    In the early days, the question was whether coaches and individuals could raise the maximum uptake so as to increase athletic performance. The answer emerged quickly: very much so. Regular aerobic training turned out to increase the size of the heart, most especially its left ventricle—the heart’s largest chamber, which pumps oxygenated