Endure. Alex Hutchinson

competitors at the end of a race? A testament to his endurance: he’s slowing down a little less (or a little later) than everyone else. In Bolt’s 9.58-second world-record race at the 2009 World Championships in Berlin, his last 20 meters was five hundredths of a second slower than the previous 20 meters, but he still extended his lead over the rest of the field.

      At the same world championships, Bolt went on to set the 200-meter world record with a time of 19.19 seconds. A crucial detail: he ran the first half of the race in 9.92 seconds—an amazing time, considering the 200 starts on a curve, but still slower than his 100-meter record. It’s barely perceptible, but he was pacing himself, deliberately spreading his energy out to maximize his performance over the whole distance. This is why the psychology and physiology of endurance are inextricably linked: any task lasting longer than a dozen or so seconds requires decisions, whether conscious or unconscious, on how hard to push and when. Even in repeated all-out weightlifting efforts—brief five-second pulls that you’d think would be a pure measure of muscular force—studies have found that we can’t avoid pacing ourselves: your “maximum” force depends on how many reps you think you have left.

      This inescapable importance of pacing is why endurance athletes are obsessed with their splits. As John L. Parker Jr. wrote in his cult running classic, Once a Runner, “A runner is a miser, spending the pennies of his energy with great stinginess, constantly wanting to know how much he has spent and how much longer he will be expected to pay. He wants to be broke at precisely the moment he no longer needs his coin.” In my race in Sherbrooke, I knew I needed to run each 200-meter lap in just under 32 seconds in order to break four minutes, and I had spent countless training hours learning the feel of this exact pace. So it was a shock, an eye-widening physical jolt to my system, to hear the timekeeper call out, as I completed my first circuit of the track, “Twenty-seven!”

      The science of how we pace ourselves turns out to be surprisingly complex (as we’ll see in later chapters). You judge what’s sustainable based not only on how you feel, but on how that feeling compares to how you expected to feel at that point in the race. As I started my second lap, I had to reconcile two conflicting inputs: the intellectual knowledge that I had set off at a recklessly fast pace, and the subjective sense that I felt surprisingly, exhilaratingly good. I fought off the panicked urge to slow down, and came through the second lap in 57 seconds—and still felt good. Now I knew for sure that something special was happening.

      As the race proceeded, I stopped paying attention to the split times. They were so far ahead of the 4:00 schedule I’d memorized that they no longer conveyed any useful information. I simply ran, hoping to reach the finish before the gravitational pull of reality reasserted its grip on my legs. I crossed the line in 3 minutes, 52.7 seconds, a personal best by a full nine seconds. In that one race, I’d improved more than my cumulative improvement since my first season of running, five years earlier. Poring through my training logs—as I did that night, and have many times since—revealed no hint of the breakthrough to come. My workouts suggested, at most, incremental gains compared to previous years.

      After the race, I debriefed with a teammate who had timed my lap splits for me. His watch told a very different story of the race. My first lap had taken 30 seconds, not 27; my second lap was 60, not 57. Perhaps the lap counter calling the splits at the finish had started his watch three seconds late; or perhaps his effort to translate on the fly from French to English for my benefit had resulted in a delay of a few seconds. Either way, he’d misled me into believing that I was running faster than I really was, while feeling unaccountably good. As a result, I’d unshackled myself from my pre-race expectations and run a race nobody could have predicted.

      After Roger Bannister came the deluge—at least, that’s how the story is often told. Typical of the genre is The Winning Mind Set, a 2006 self-help book by Jim Brault and Kevin Seaman, which uses Bannister’s four-minute mile as a parable about the importance of self-belief. “[W]ithin one year, 37 others did the same thing,” they write. “In the year after that, over 300 runners ran a mile in less than four minutes.” Similar larger-than-life (that is, utterly fictitious) claims are a staple in motivational seminars and across the Web: once Bannister showed the way, others suddenly brushed away their mental barriers and unlocked their true potential.

      As interest in the prospects of a sub-two-hour marathon heats up, this narrative crops up frequently as evidence that the new challenge, too, is primarily psychological. Skeptics, meanwhile, assert that belief has nothing to do with it—that humans, in their current form, are simply incapable of running that fast for that long. The debate, like its predecessor six decades ago, offers a compelling real-world test bed for exploring the various theories about endurance and human limits that scientists are currently investigating. But to draw any meaningful conclusions, it’s important to get the facts right. For one thing, Landy was the only other person to join the sub-four club within a year of Bannister’s run, and just four others followed the next year. It wasn’t until 1979, more than twenty years later, that Spanish star José Luis González became the three hundredth man to break the barrier.

      And there’s more to Landy’s sudden breakthrough, after being stuck for so many races, than simple mind over muscle. His six near-misses all came at low-key meets in Australia where competition was sparse and weather often unfavorable. He finally embarked on the long voyage to Europe, where tracks were fast and competition plentiful, in the spring of 1954—only to discover, just three days after he arrived, that Bannister had already beaten him to the goal. In Turku, he had a pacer for the first time, a local runner who led the first lap and a half at a brisk pace. And more important, he had real competition: Chris Chataway, one of the two men who had paced Bannister’s sub-four run, was nipping at Landy’s heels until partway through the final lap. It’s not hard to believe that Landy would have broken four that day even if Roger Bannister had never existed.

      Still, I can’t entirely dismiss the mind’s role—in no small part because of what happened in the wake of my own breakthrough. In my next attempt at the distance after Sherbrooke, I ran 3:49. In the race after that, I crossed the line, as confused as I was exhilarated, in 3:44, qualifying me for that summer’s Olympic Trials. In the space of three races, I’d somehow been transformed. The TV coverage of the 1996 trials is on YouTube, and as the camera lingers on me before the start of the 1,500 final (I’m lined up next to Graham Hood, the Canadian record-holder at the time), you can see that I’m still not quite sure how I got there. My eyes keep darting around in panic, as if I expect to glance down and discover that I’m still in my pajamas.

      I spent a lot of time over the next decade chasing further breakthroughs, with decidedly mixed results. Knowing (or believing) that your ultimate limits are all in your head doesn’t make them any less real in the heat of a race. And it doesn’t mean you can simply decide to change them. If anything, my head held me back as often as it pushed me forward during those years, to my frustration and befuddlement. “It should be mathematical,” is how U.S. Olympic runner Ian Dobson described the struggle to understand the ups and downs of his own performances, “but it’s not.” I, too, kept searching for the formula—the one that would allow me to calculate, once and for all, my limits. If I knew that I had run as fast as my body was capable of, I reasoned, I’d be able to walk away from the sport with no regrets.

      At twenty-eight, after an ill-timed stress fracture in my sacrum three months before the 2004 Olympic Trials, I finally decided to move on. I returned to school for a journalism degree, and then started out as a general assignment reporter with a newspaper in Ottawa. But I found myself drawn back to the same lingering questions. Why wasn’t it mathematical? What held me back from breaking four for so long, and what changed when I did? I left the newspaper and started writing as a freelancer about endurance sports—not so much about who won and who lost, but about why. I dug into the scientific literature and discovered that there was a vigorous (and sometimes rancorous) ongoing debate about those very questions.

      Physiologists spent most of the twentieth century on an epic quest to understand how our bodies fatigue. They cut the hind legs off frogs and jolted the severed muscles with electricity until they stopped twitching; lugged cumbersome lab equipment on expeditions to remote Andean peaks; and pushed thousands of volunteers to exhaustion on treadmills, in heat chambers, and on every drug you can think of. What emerged was