Endure: Mind, Body and the Curiously Elastic Limits of Human Performance. Alex Hutchinson

My next split was a disappointing 2:53. That was as fast as I could move my legs, and my pace slowed even more as I entered the final kilometer. I’d bitten off more than I could chew and was paying the price.

      At most track races, officials mark the start of your final 400-meter lap by ringing a cowbell in your ear. It’s a handy Pavlovian cue that tells you that your suffering is almost over. And on that night on the Stanford track, I once again felt the curious and familiar transformation in my legs as the bell rang for me. I passed ten runners while running the last lap in around 57 seconds, a full 10 seconds faster than my average pace for the race. My last kilometer, at 2:42, was my fastest even though I only started sprinting with a lap to go. And—I can’t emphasize this enough—I was trying as hard as I could right up to the penultimate lap. A friend who’d come to watch asked if I was trying to impress her by slowing down late in the race so I could finish with a flourish. No, I said, I just … But I didn’t have an explanation. I didn’t understand it myself.

      As it turns out, it’s not just me. Noakes showed me a study that he, Tucker, and Michael Lambert had published in 2006, analyzing the pacing patterns of almost every world record set in the modern era in the men’s 800 meter, mile, 5,000, and 10,000 meter races. For the three longer races, the pattern was startlingly consistent: after a quick start, the record breakers would settle into a steady pace until the final stages of the race. Then, even though they were running faster than they’d ever run before, and their oxygen-starved muscles were presumably awash in a sea of fatigue-inducing metabolites, they accelerated. Of the 66 world records in the 5,000 and 10,000 meters dating back to the early 1920s, the last kilometer was either the fastest of the race or the second fastest (behind the opening kilometer) in all but one. I was willing to attribute my own uneven pacing to incompetence—but these were the finest runners in history on the best day of their lives, which suggests that the pattern is more deeply ingrained than a mere pacing error.

      In fact, there’s good reason to think that pacing is driven as much by instinct as by choice, according to Dominic Micklewright, a researcher at the University of Essex. Micklewright followed an unorthodox route to academia, going straight from high school to the Royal Navy, where he served as a diver on nuclear submarines for seven years, and then spending nine years as a police officer in London before studying sport and exercise psychology. His interest in pacing dates back to his training as a military diver, when he and the other trainees had to swim submerged to the other end of a 1,200-meter saltwater lake on Horsea Island, on Britain’s south coast, without using up their supply of air. “If they caught you breaching, you would get clobbered over the back of the head with an oar, or they’d throw in one of those underwater scare charges,” he recalls. With that incentive, you inevitably thought very carefully about the challenge of spending your energy—and oxygen—as frugally as possible.

World records in long-distance races are run with a strikingly consistent pattern that includes an acceleration in the final stages, according to a 2006 analysis in the International Journal of Sports Physiology and Performance. This finishing kick is notably absent in shorter 800-meter races, for reasons we’ll discuss in Chapter 6. The intermediate splits above are every 400 meters for the two shorter races, and every 1,000 meters for the two longer ones.

      In 2012, Micklewright had more than a hundred schoolchildren ranging in age from five to fourteen complete a battery of tests to assess their cognitive development, in order to slot them into one of the four developmental stages proposed by Swiss psychologist Jean Piaget; then the kids ran a race lasting about four minutes. The younger kids in the two lower Piaget stages opted for the unfettered sprint-and-then-hang-on-for-dear-life approach, starting fast then steadily fading. In contrast, the kids in the two higher Piaget stages had already adopted the familiar U-shaped pacing profile that world-record holders use: a fast start, gradual slowing, then a fast finish. Sometime around the age of eleven or twelve, in other words, our brains have already learned to anticipate our future energy needs and hold back something in reserve—a relic, Micklewright speculated, of the delicate balance between searching for food and conserving energy deep in our evolutionary past.

      Not everyone buys Noakes’s argument that pacing patterns like the end spurt reveal the workings of a central governor. For example, it could be that you speed up at the end of a race because you finally tap into your precious but limited reserves of anaerobic energy, the high-octane fuel source that powers you in short races lasting less than a minute. But there are other hints that the finishing kick isn’t just physiological.

      In 2014, a group of economists from the University of Southern California; the University of California, Berkeley; and the University of Chicago mined a massive dataset containing the finish times of more than nine million marathoners from races around the world spanning four decades. The distribution of finishing times looks a bit like the classic bell-shaped curve, but with a set of spikes superimposed. Around every significant time barrier—three hours, four hours, five hours—there are far more finishers than you’d expect just below the barrier, and fewer than you’d expect just above. Similar but smaller spikes show up at half-hour intervals, and there are barely perceptible ripples even at ten-minute increments. The cruel metabolic demands of the marathon, which inevitably depletes your stores of readily available fuel, mean that most people are slowing in the final miles. But with the right incentive, some are able to speed up—and it’s only the brain that can respond to abstract incentives like breaking four hours for an arbitrary distance like 26.2 miles.

      A further curious detail from this dataset: the faster the runners were, the less likely they were able to summon a finishing sprint. Of the runners finishing near the three-hour barrier, about 30 percent were able to speed up in the final 1.4 miles of the race; 35 percent of those trying to break four hours sped up; and more than 40 percent of those trying to break five hours managed it. One possible interpretation is that, over the course of their long hours of training, the more committed runners had gradually readjusted the settings on their central governors, learning to leave as little as possible in reserve. Perhaps that’s another, slower way of achieving the run-in-the-present-moment strength that allows Diane Van Deren to race so close to her limits. I tried to trick myself into forgetting the last kilometer of my 5,000-meter races; Van Deren’s bittersweet gift is that she can forget without even trying.

      Right from the start, the central governor proposal was highly controversial. After his 1996 speech, Noakes recalls, “people got very, very angry.” There were rebuttals and surrebuttals in a cycle that is still continuing, more than two decades later. In a 2008 article in the British Journal of Sports Medicine, Noakes argued that physiologists’ focus on VO₂max had “produced a brainless model of human exercise performance.” Roy Shephard, an influential professor emeritus at the University of Toronto, shot back with an article in the journal Sports Medicine in 2009 titled “Is It Time to Retire the ‘Central Governor’?” Following a further exchange, Shephard concluded, “In the parlance of my North American colleagues, the time may now be ripe for proponents of the hypothesis to ‘Put up or shut up.’”

      If anything, the controversies swirling around Noakes have increased since his retirement from the University of Cape Town in 2014. His book on hydration, Waterlogged, accused most of the world’s leading hydration researchers, including former colleagues and collaborators, of selling out to the commercial interests of sports-drink makers. He is now a vocal proponent of low-carb, high-fat diets for both health and athletic performance, leading him to disown the chapters he wrote on nutrition and carbohydrate loading in Lore of Running and earning him a disciplinary hearing that threatened to revoke his medical