The Science of Yoga

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 blood into the arteries and body. A bigger left ventricle sent out more blood per beat and more oxygen to the tissues and muscles. Scientists sought to measure the rise. It turned out that the cardiac output of elite athletes was about twice that of untrained individuals.
    The benefits extended to most anyone who took up vigorous exercise. In time, scientists found that three months of endurance training could raise VO 2 max between 15 and 30 percent. Two years raised it as much as 50 percent.
    The new perspective was a breakthrough. At last, after many decades of mistakes and misapprehensions, scientists had uncovered what seemed like a dependable guide to human fitness.
    The topic was long obscure. Then Kenneth H. Cooper came along. A track star in his native Oklahoma, the physician worked for the Air Force and early in his career devised a simple test that provided a good estimate of an individual’s VO 2 max. The test measured how far a person could run in twelve minutes. Cooper’s rule of thumb let the Air Force quickly assess the fitness of new recruits. Eager to popularize his insights, he invented a new word, “aerobics,” and in 1968 authored a book by the same name. It drew on his years of research to show what kinds of exercise produced the best cardiovascular workout. Cooper found that such muscular activities as calisthenics and weightlifting were the least effective. Participant sports like golf and tennis came in second. And the big winners? Challenging sports like running, swimming, and cycling, as well as vigorous participant sports such as handball, squash, and basketball. His analyses caught on rapidly and helped get millions of people off their chairs and into the streets. Starting in the