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Book Summary: Endure – Mind, Body, and the Curiously Elastic Limits of Human Performance

Endure (2018) takes an in-depth look at what enables certain boundary-pushing athletes to hit the wall of pain and effort – and still keep going. Alex Hutchinson examines the multiple and complex factors that allow marathon runners and cyclists to keep breaking records and reaching new heights in human endurance.

Who is it for?

  • Athletes and coaches
  • Students of psychology and sports medicine
  • Anyone training for a marathon

Find out what it really means to hit the wall of human endurance.

There’s a good chance you can summon a vivid image of a marathon runner crossing the finish line and then collapsing to the ground, visibly shaking, covered in sweat and barely able to function. You may have asked yourself, “How did they make it over the line? What kept them from collapsing a few minutes earlier?”

These are similar to the questions that have been on the mind of the author, Alex Hutchinson, ever since his grad-student days when he was running for the Canadian national team. Since then, Hutchinson has become an expert on endurance sports and finding out how we’re able to push our bodies to the limit, climb to the top of the highest mountains and cross those seemingly insurmountable boundaries of pain and effort.

Along the way, Hutchinson has unearthed intriguing science on just how far we’ve come toward understanding the biology of endurance, especially as it pertains to the involvement of the brain. In recent years, it’s become increasingly clear that the mind plays a very large instinctual role in telling the body when to pace itself and when to shut down. As Hutchinson has found, something as seemingly uncomplicated as running or riding a bike is, in fact, a fascinatingly complex process.

Book Summary: Endure - Mind, Body, and the Curiously Elastic Limits of Human Performance

In these summaries, you’ll discover

  • what eleven-year-olds can tell us about marathon runners;
  • why you should avoid thinking too hard before a physical competition; and
  • why a marathon at the Dead Sea would likely produce record-breaking results.

Trying to test the limits of human endurance can have fatal consequences.

The British explorer Henry Worsley liked to test the limits of human endurance. Or perhaps it’s more accurate to say that he liked to push himself beyond the normal boundaries and set new limits.

One such boundary-pushing expedition began in late 2015 when Worsley attempted to walk across Antarctica all by himself. He made it a full 56 days before the journey began taking a dangerous toll on his body.

On the night of the 56th day, painful indigestion kept him from getting any sleep. So the next day Worsley tried to rest, but with 200 miles still to go, he couldn’t afford to take too much time off.

At midnight, with the polar sun still beating down upon him, he resumed his journey, the current leg of which involved climbing up the Titan Dome – a mountain of ice that peaked at 3,100 meters above sea level. Every step of the way, Worsley faced strong headwinds that drove sheets of snow against him as he gasped for breath in the thinning air. After 16 hours, Worsley had to stop for another break.

While Worsley was walking solo, he did have a satellite phone with him in case he had to call for help. This was something of a double-edged sword; it could save his life in an emergency, but it also gave him so much security that he was pushing his body far past any reasonable limit. Since his journey began, he’d already lost 48 pounds in bodyweight.

Remarkably, Worsley would last over another week before he finally used the phone to call his rescue team. At that point, he’d been walking for 70 days and was just 30 miles away from his goal.

The next day, Worsley was picked up and flown to a hospital in Punta Arenas, Chile, where he was quickly diagnosed with dehydration and exhaustion. But that wasn’t all. The doctors found signs of bacterial peritonitis, an abdominal infection that required immediate surgery – and things quickly took a turn for the worse.

The infection proved too much for Worsley’s weakened body, and on January 24, 2016, his organs shut down, and he died. This tragic death raised some important questions about the ethical and practical limits of such boundary-pushing expeditions.

It’s true that humans have safely returned from some unbelievable places, and in the summaries ahead we’ll look at the human body’s limitations, and why some feats are possible, while others simply aren’t.

We instinctively pace ourselves for that final push in long-distance running.

While the author was working on his PhD, he ran middle- and long-distance races for the Canadian national team. At one point, he noticed that he ran faster at the end of the race, even though this wasn’t part of his strategy. And it led to his wondering whether this happened to everyone.

In 2006, researchers Tim Noakes and Michael Lambert published a study of the patterns they found among the world’s greatest long-distance runners.

Their findings showed a consistent pattern: after starting off fast, the best runners would then decrease their speed for the longer mid-portion of the race and accelerate at the end – even though one might assume that their energy resources would be depleted by that point.

A casual observer would likely think that this pattern is a tactical decision, but it’s likely an evolutionary response in our brain.

At the University of Essex, sports scientist Dominic Micklewright wanted to learn more about our ability to pace ourselves, and he wondered whether it was an instinct we develop at a certain time in our lives. Micklewright’s curiosity was also inspired by Swiss psychologist Jean Piaget, who found that childhood development was made up of distinct behavioral phases.

So, in 2012, while working with children from age five to 14, Micklewright tried to determine when we develop our ability to pace ourselves. He found that the majority of the younger children (those under the age of eleven) would sprint at the start and then run slower and slower as the race went on. Meanwhile, children eleven and older would pace themselves according to the pattern of world-record holders, by slowing down in the mid-section before finishing with a sprint.

According to both Micklewright and fellow sports scientist Tim Noakes, this pacing pattern is not a strategy, but rather an instinctual response programmed into the human brain. They believe it’s related to our time as hunter-gatherers and that it developed as a way for us to run long distances while hunting and to reserve energy in case we need to finish the hunt with a final burst of speed.

Having a tired brain can affect your physical endurance.

In 2013, Samuele Marcora traveled over six and a half thousand miles on his motorcycle, from London to Beijing, an endurance test that doubled as a continuation of his long-term study into the mental component of physical effort.

Indeed, the trip reinforced Marcora’s belief that the mind plays a big part in how much we can endure. In other words, fatigue isn’t just a physiological experience.

In 2009, Marcora conducted a study that asked one half of a group to play a mentally challenging computer game for 90 minutes. The other half were tasked with watching a pleasant 90-minute documentary, such as The History of Ferrari.

When the 90 minutes were up, all participants were then asked to exercise on a stationary bicycle until they reached exhaustion. The participants who’d just watched television lasted, on average, 15.1 percent longer than those who’d played the computer game. Since there was no physiological difference between the groups, the results suggest that the mental fatigue of the complex computer game caused the participants who’d played it to become exhausted sooner.

Marcora’s study also supports the theory that perceived effort is a significant factor in endurance.

The study of perceived effort goes back to the 1960s when the Swedish psychologist Gunnar Borg began to study and measure this quality. Borg set a scale of six to 20, with six being the least amount of perceived effort a person can give, and 20 the maximum.

Borg’s research upended the prevailing scientific understanding of endurance at the time, which treated the body like any other machine, in that it continued functioning as long as the mechanics were operational – which, in this case, would be the muscles. On this mechanistic view, feelings of exhaustion are purely due to physical effort.

However, Marcora’s model took Borg’s findings a step further. He pinpoints an athlete’s total exhaustion as being the combination of muscle fatigue, which creates the initial feeling of mounting effort, and the person reaching their maximum threshold of perceived effort. Where muscle fatigue and perceived-effort threshold intersect is when all effort must stop.

Taking perceived effort into account makes a big difference because it can be influenced by a number of different mental factors, including how motivated a person is and the subliminal messages they may be picking up on.

Athletes have a tolerance for pain that’s higher than normal, which improves performance.

Veteran cyclist Jens Voigt has worn the Tour de France yellow jersey twice, having been in the lead in the race. But Voigt is also famous for his love of physical suffering. As he puts it, pain is just a weakness to be overcome.

Voigt’s perspective may sound extreme, but there are many athletes who would likely agree. And it’s probably this willingness to suffer that accounts for the fact that athletes’ pain thresholds have been shown to be higher than average people’s.

One of the first studies of athletes’ pain perception was conducted in 1981 by psychologist Karel Gijsbers, who compared the pain tolerance of elite swimmers with those of amateur swimmers.

Dr. Gijsbers measured pain by pumping up a blood-pressure monitor and stopping the blood circulation in a participant’s arm. As he did this, participants were told to clench and open their fist once every second. Their pain threshold was marked as the moment they first reported feeling pain, and the maximum tolerance was the instant they asked to stop.

All participants had a similar pain threshold, but the elite swimmers could continue contracting fists for far longer than the amateur ones. On average, the hobbyists could make 89 fists while the athletes could make 132.

So the question then becomes, why can athletes endure more pain? Subsequent studies by Dr. Gijsbers suggest that it is due to training. By performing tests throughout the swimming season, Gijsbers found that the overall pain tolerance was at its highest when their training was at its peak, during the month of June.

And that’s not all. A related study from Oxford Brookes University shows that increased pain tolerance goes hand in hand with increased athletic performance.

In fact, athletes whose training regimen was made up of short bursts of high intensity, and therefore high pain, made more progress than those who trained longer but with less intensity. This means that the more tolerance for pain an athlete can endure in their training, the more benefits they’ll experience in their performance.

However, good performance involves more than just an ability to tolerate pain, as we’ll discover in the next chapter.

Oxygen intake is a key factor in athletic performance.

A good coach can be a valuable asset to any athlete. And if there’s one piece of advice that every coach will give, it’s to breathe, breathe, breathe.

This is extremely important advice because the amount of oxygen you take in directly influences how well you perform.

Athletes can measure the maximum amount of oxygen intake during training through what is known as VO2 max, which stands for volume, oxygen, maximum. The general rule of thumb is, the more oxygen a person can take in, and therefore circulate through their body, the better they’ll perform – especially in an endurance sport like running a marathon.

So it’s no coincidence that Norway’s Bjorn Daehlie won multiple cross-country skiing awards in the 1990s, while also holding the record for the highest VO2 max ever measured. Daehlie topped out at 96 milliliters of oxygen per kilogram of body mass per minute. This is a massive amount since the average human capacity is 35 ml/kg/min.

Of course, VO2 max isn’t an absolute indicator of athletic performance. Another Norwegian athlete, Oskar Svendsen, beat Daehlie’s record with a VO2 max of 97.5 ml/kg/min. However, as a cyclist, Svendsen retired early after a spotty career.

Oxygen intake is also the reason behind athletes exhibiting better performances at low altitudes. Simply put, the lower the altitude, the more oxygen there is available.

Canberra University is located in Australia, and it’s situated at an elevation of 577 meters above sea level. According to the school’s own study, this was high enough to significantly reduce the VO2 max levels, and it’s why the runners at the school produced slower times.

Conversely, when runners are in an atmosphere rich in oxygen, they’re in a better position to beat their own personal best and set new world records. Scientist Yannis Pitsiladis has recommended that a marathon be held around the Dead Sea, which is 400 meters below sea level. He suggests that this could be the solution to finally having a runner overcome the challenge of completing a marathon in under two hours.

Core body temperature also influences endurance.

One of the more dangerous risks for athletes is heat stroke, which has proved deadly for both professionals and amateurs alike.

Avoiding it is one reason why athletes pay close attention to the temperature inside their body, otherwise known as their core temperature. But the other reason is that science has shown a very real link between core temperature and endurance.

More precisely, an athlete’s core temperature is a strong indicator of how much more they’ll be able to endure.

This link was the basis for a 1999 study by José Gonzalez-Alonso of Copenhagen University. He monitored seven athletes who were told to exercise on stationary bicycles until they reached exhaustion. Before they began, the athletes bathed for 30 minutes in water that was either 36, 37 or 38 degrees Celsius.

As it turned out, the cyclists with a 36-degree core temperature lasted twice as long as those who had been heated up to 38 degrees. In fact, the study showed that every participant called it quits when their core temperature reached between 40.0 and 40.3 degrees.

Unsurprisingly, this study was a big influence on the 2004 Olympics in Athens, where coaches began using cooling basins to bring down their athlete’s core temperature before a competition.

Since then, there’s been some research into which area affects core temperature the most: the brain or the stomach?

In the 2008 Olympics, some athletes were downing an ice slushy before competing, as melting ice in the stomach was found to lower core temperature by as much as 0.7 degrees Celsius. The slushies also seemed to give athletes the ability to push their core temperature slightly higher before exhaustion – to be exact, by around one-third of a degree.

So why does this work? Scientists believe that when an athlete competes after drinking the ice slushy, their body warms up first, but the system doesn’t shut down until the brain reaches that critical temperature.

However, the data is still inconclusive. One possibility is that the temperature sensors in the stomach are critical for the shutdown signal to the brain, and drinking the slushy delays this signal.

At the time of writing, neither hypothesis has yet been confirmed.

Mindfulness can lessen stress levels and improve athletic performance.

As we’ve seen, the mind plays a bigger role in physical endurance than was commonly believed among previous generations of sports scientists. But in the East, the mind has traditionally been at the center of athletic mastery, especially in sports such as martial arts.

Only recently have Westerners begun to look to Eastern philosophies like mindfulness for insights into achieving higher levels of endurance.

Mindfulness is generally described as giving focused attention to any given action, and its introduction to Western training programs is credited to German neuroscientist Martin Paulus. He was especially interested in the effect it had on the stress levels of soldiers.

Dr. Paulus used the mindfulness concept of Zen Buddhism, as taught by Jon Kabat-Zinn, who developed a structured eight-week program aimed to lower stress levels. He believed that reduced stress would help soldiers function better in high-pressure situations.

In a 2016 study, Dr. Paulus tested the results of his efforts on soldiers near San Diego, California. The soldiers had their brain activity measured while being scanned in a claustrophobic MRI machine. While this was being done, the supply of oxygen to the soldiers was altered in unpredictable ways, at times making it difficult to breathe.

The results showed that the soldiers who’d been untrained in mindfulness were likely to panic when the oxygen supply diminished, which then led to a peak of activity in the stress-related insular cortex region of the brain. However, after spending eight weeks in mindfulness training, the soldiers no longer panicked, and the activity in their insular cortex remained stable.

So there’s hope that mindfulness will help soldiers better cope with stressors on the field. In the meantime, it’s already proven effective in reducing the symptoms of post-traumatic stress disorders.

On top of this, Dr. Paulus has developed a mindfulness program tailored to athletes, with emphasis on embracing pain, concentration and self-compassion.

While the results haven’t been conclusively measured, the US Olympic BMX Team have already reported measured improvements in their performance. Their racing times have improved, and the athletes have mentioned feeling more conscious of their bodies during activities.

The areas of the brain most related to endurance are the insular and motor cortices.

We’ve all felt exhausted. But relatively few people know what the precise process is that causes us to hit a certain point and experience a full-body shutdown.

While scientists have spent decades looking into exhaustion as a purely physical reaction, neuropsychologist Kai Lutz was the first to think of looking at exhaustion from within the brain.

What he found was that the first regions of the brain to recognize the onset of exhaustion are the insular cortex and then the motor cortex.

Dr. Lutz discovered this through the use of EEG scans, which stands for electroencephalography, a technique that tracks the brain’s electrical wave patterns. He used this on cyclists who pedaled at high speeds until hitting the wall of exhaustion at around the 40-minute mark.

Dr. Lutz noticed that shortly before the cyclists gave up, the insular cortex was activated. This region is found at the center of the cerebral cortex and the brain itself. And immediately after is was activated, it sent a signal to the motor cortex, which controls the muscles, and this resulted in the athletes calling it quits soon afterward.

Seeing that they anticipated the collapse of the muscles, it is fair to call these two cortices the brain’s endurance center. However, it remains unclear as to how much influence we can have over the endurance center.

Dr. Lutz’s study suggests that we may be able to suppress the sensitivity of the neurons in the insular cortex, thereby delaying the message to the motor cortex and, therefore, the muscles. This hypothesis was later tested in 2015 by another neurophysiologist: Alexandre Okano from the University of Rio Grande.

In Dr. Okano’s study, cyclists were hooked up to electrodes that directly activated the insular cortex with transcranial direct-current stimulation. After 20 minutes of this stimulation, cyclists improved their racing time by around 4 percent before reaching exhaustion.

Another theory is to continually stimulate the neurons of the motor cortex so that this activity would effectively block the signal from the insular cortex. While this sounds promising, it has yet to be proven successful.

The practice of transcranial direct-current stimulation is still in its rudimentary stages, and scientists are unable to deliver stimulation with pinpoint accuracy. As a result, by targeting the motor cortex, other parts of the brain, including the insular cortex, are affected.

Nevertheless, these studies show that tremendous progress has been made toward better understanding human endurance, even though we may still have a way to go before we have complete control.

Final Summary

The key message in these summaries:

Endurance is a fascinating human phenomenon that involves much more than pure muscle power. There are, in fact, many physiological elements at play, including core body temperature and our capacity for oxygen intake, as well as psychological factors, like perceived effort and our tolerance for pain. All of these play a significant role in the kind of athletic performance we are capable of, especially when it comes to setting new world records in marathon running, cross-country skiing and other feats of endurance.

Actionable advice:

If a method works, use it, even if evidence suggests it’s just a placebo.

Almost all athletes report better recovery from physical exertion after taking an ice-bath following their competition. Yet studies show that this practice has no direct beneficial effect on inflammation levels, which is what the baths are intended to reduce. But if there’s a procedure that helps you recover, even if it’s purely psychological, there is no reason to dismiss it. Sometimes belief is just as important as science.

About the author

Alex Hutchinson is an award-winning journalist and contributing editor to Outside magazine. His work has also been featured in the New Yorker, the New York Times, the Globe and Mail and Runner’s World. With a PhD in physics from the University of Cambridge, as well as a true passion for the outdoors and running, he is uniquely qualified to research the science behind fitness and endurance.

Alex Hutchinson, Ph.D., is a columnist for Outside magazine and was a long-time columnist for Runner’s World. A National Magazine Award winner, he is a regular contributor to The New Yorker online, pens the weekly “Jockology” column in the Toronto Globe and Mail, and writes for the New York Times. FiveThirtyEight recently named him one of their “favorite running science geeks.” He was a two-time finalist in the 1,500 meters at the Canadian Olympic Trials, and represented Canada internationally in track, cross-country, road racing, and mountain running competitions. He holds a Ph.D. in physics from the University of Cambridge, and has worked as a researcher for the U.S. National Security Agency. He lives in Toronto, Canada.


Science, Math, Biological Sciences, Health, Fitness, Exercise, Sport, Recreation, Running, Jogging, Sport Psychology, Self-Help, Personal Development, Biology


THE NEW YORK TIMES BESTSELLER • Foreword by Malcolm Gladwell

Limits are an illusion: discover the revolutionary account of the science and psychology of endurance, revealing the secrets of reaching the hidden extra potential within us all.

The capacity to endure is the key trait that underlies great performance in virtually every field. But what if we all can go farther, push harder, and achieve more than we think we’re capable of?

Blending cutting-edge science and gripping storytelling in the spirit of Malcolm Gladwell—who contributes the book’s foreword—award-winning journalist Alex Hutchinson reveals that a wave of paradigm-altering research over the past decade suggests the seemingly physical barriers you encounter as set as much by your brain as by your body. This means the mind is the new frontier of endurance—and that the horizons of performance are much more elastic than we once thought.

But, of course, it’s not “all in your head.” For each of the physical limits that Hutchinson explores—pain, muscle, oxygen, heat, thirst, fuel—he carefully disentangles the delicate interplay of mind and body by telling the riveting stories of men and women who’ve pushed their own limits in extraordinary ways.

The longtime “Sweat Science” columnist for Outside and Runner’s World, Hutchinson, a former national-team long-distance runner and Cambridge-trained physicist, was one of only two reporters granted access to Nike’s top-secret training project to break the two-hour marathon barrier, an extreme quest he traces throughout the book. But the lessons he draws from shadowing elite athletes and from traveling to high-tech labs around the world are surprisingly universal. Endurance, Hutchinson writes, is “the struggle to continue against a mounting desire to stop”—and we’re always capable of pushing a little farther.

Read an Excerpt

From the Back Cover


The capacity to endure is the key trait that underlies great performance in virtually every field—from a 100-meter sprint to a 100-mile ultramarathon, from summiting Everest to acing final exams or completing any difficult project. But what if we all can go farther, push harder, and achieve more than we think we’re capable of?

Blending cutting-edge science and gripping storytelling in the spirit of Malcolm Gladwell—who contributes the book’s foreword—award-winning journalist Alex Hutchinson reveals that a wave of paradigm-altering research over the past decade suggests the seemingly physical barriers you encounter are set as much by your brain as by your body. This means the mind is the new frontier of endurance—and that the horizons of performance are much more elastic than we once thought.

But, of course, it’s not “all in your head.” For each of the physical limits that Hutchinson explores—pain, muscle, oxygen, heat, thirst, fuel—he carefully disentangles the delicate interplay of mind and body by telling the riveting stories of men and women who’ve pushed their own ultimate limits in extraordinary ways.

The longtime “Sweat Science” columnist for Outside and Runner’s World, Hutchinson, a former national-team long-distance runner and Cambridge-trained physicist, was one of only two reporters granted access to Nike’s top-secret training project to break the two-hour marathon barrier, an extreme quest he traces throughout the book. But the lessons he draws from shadowing elite athletes and from traveling to high-tech labs around the world are surprisingly universal. Endurance, Hutchinson writes, is “the struggle to continue against a mounting desire to stop”—and we’re always capable of pushing a little farther.

Part I: Mind and Muscle
Chapter 1 The Unforgiving Minute
If you can fill the unforgiving minute With sixty seconds’ worth of distance run, Yours is the Earth and everything that’s in it. . . . — Rudyard Kipling

On a frigid Saturday night in the university town of Sherbrooke, Quebec, in February 1996, I was pondering—yet again—one of the great enigmas of endurance: John Landy. The stocky Australian is one of the most famous bridesmaids in sport, the second man in history to run a sub-four-minute mile. In the spring of 1954, after years of concerted effort, centuries of timed races, millennia of evolution, Roger Bannister beat him to it by just forty-six days. The enduring image of Landy, immortalized in countless posters and a larger-than-life bronze statue in Vancouver, British Columbia, comes from later that summer, at the Empire Games, when the world’s only four-minute milers clashed head-to-head for the first and only time. Having led the entire race, Landy glanced over his left shoulder as he entered the final straightaway—just as Bannister edged past on his right. That split-second tableau of defeat confirmed him as, in the words of a British newspaper headline, the quintessential “nearly man.”

But Landy’s enigma isn’t that he wasn’t quite good enough. It’s that he clearly was. In pursuit of the record, he had run 4:02 on six different occasions, and eventually declared, “Frankly, I think the four-minute mile is beyond my capabilities. Two seconds may not sound much, but to me it’s like trying to break through a brick wall.'” Then, less than two months after Bannister blazed the trail, Landy ran 3:57.9 (his official mark in the record books is 3:58.0, since times were rounded to the nearest fifth of a second in that era), cleaving almost four seconds off his previous best and finishing 15 yards ahead of four-minute pace—a puzzlingly rapid, and bittersweet, transformation.

Like many milers before me and since, I was a Bannister disciple, with a creased and nearly memorized copy of his autobiography in permanent residence on my bedside table; but in that winter of 1996 I was seeing more and more Landy when I looked in the mirror. Since the age of fifteen, I’d been pursuing my own, lesser four-minute barrier—for 1,500 meters, a race that’s about 17 seconds shorter than a mile. I ran 4:02 in high school, and then, like Landy, hit a wall, running similar times again and again over the next four years. Now, as a twenty-year-old junior at McGill University, I was starting to face the possibility that I’d squeezed out every second my body had to offer. During the long bus ride from Montreal to Sherbrooke, where my teammates and I were headed for a meaningless early-season race on one of the slowest tracks in Canada, I remember staring out the window into the swirling snow and wondering if my long-sought moment of Landyesque transformation would ever arrive.

The story we’d heard, possibly apocryphal, was that the job of designing the Sherbrooke indoor track had been assigned to the university’s engineering department as a student project.

Tasked with calculating the optimal angles for a 200-meter track, they’d plugged in numbers corresponding to the centripetal acceleration experienced by world-class 200-meter sprinters—forgetting the key fact that some people might want to run more than one lap at a time. The result was more like a cycling velodrome than a running track, with banks so steep that even most sprinters couldn’t run in the outside lanes without tumbling inward. For middle-distance runners like me, even the inside lane was ankle-brealcingly awkward; races longer than a mile had to be held on the warm-up loop around the inside of the track.

To break four minutes, I would need to execute a perfectly calibrated run, pacing each lap just two-tenths of a second faster than my best time of 4:01.7. Sherbrooke, with its amusement-park track and an absence of good competition, was not the place for this supreme effort, I decided. Instead, I would run as easily as possible and save my energy for the following week. Then, in the race before mine, I watched my teammate Tambra Dunn sprint fearlessly to an enormous early lead in the women’s 1,500, click off lap after metronomic lap all alone, and finish with a scorching personal best time that qualified her for the national collegiate championships. Suddenly my obsessive calculating and endless strategizing seemed ridiculous and overwrought. I was here to run a race; why not just run as hard as I could?

Reaching the “limits of endurance” is a concept that seems yawningly obvious, until you actually try to explain it. Had you asked me in 1996 what was holding me back from sub-four, I would have mumbled something about maximal heart rate, lung capacity, slow-twitch muscle fibers, lactic acid accumulation, and various other buzzwords I’d picked up from the running magazines I devoured. On closer examination, though, none of those explanations hold up. You can hit the wall with a heart rate well below max, modest lactate levels, and muscles that still twitch on demand. To their frustration, physiologists have found that the will to endure can’t be reliably tied to any single physiological variable.

Part of the challenge is that endurance is a conceptual Swiss Army knife. It’s what you need to fmish a marathon; it’s also what enables you to keep your sanity during a cross-country flight crammed into the economy cabin with a flock of angry toddlers. The use of the word endurance in the latter case may seem metaphorical, but the distinction between physical and psychological endurance is actually less clear-cut than it appears. Think of Ernest Shackleton’s ill-fated Antarctic expedition, and the crew’s two-year struggle for survival after their ship, the Endurance, was crushed in the ice in 1915.4 Was it the toddlers-on-a-plane type of endurance that enabled them to persevere, or straightforward physical fortitude? Can you have one without the other?

A suitably versatile definition that I like, borrowing from researcher Samuele Marcora, is that endurance is “the struggle to continue against a mounting desire to stop.”‘ That’s actually Marcora’s description of “effort” rather than endurance (a distinction we’ll explore further in Chapter 4), but it captures both the physical and mental aspects of endurance. What’s crucial is the need to override what your instincts are telling you to do (slow down, back off, give up), and the sense of elapsed time. Taking a punch without flinching requires self-control, but endurance implies something more sustained: holding your finger in the flame long enough to feel the heat; filling the unforgiving minute with sixty seconds’ worth of distance run.

The time that elapses can be seconds, or it can be years. During the 2015 National Basketball Association playoffs, LeBron James’s biggest foe was —with all due respect to Golden State defender Andre Iguodala—fatigue.6 He’d played 17,860 minutes in the preceding five seasons, more than 2,000 minutes ahead of anyone else in the league. In the semis, he surprisingly asked to be pulled from a game during a tense overtime period, changed his mind, drained a three-pointer followed by a running jumper with 12.8 seconds left to seal the victory, then collapsed to the floor in a widely meme-ified swoon after the buzzer. By Game 4 of the finals, he could barely move: “I gassed out,” he admitted after being held scoreless in the final quarter. It’s not that he was acutely out of breath; it was the steady drip of fatigue accumulating over days, weeks, and months that just as surely pushed James to the limits of his endurance.

At the opposite end of the spectrum, even the greatest sprinters in the world fight against what John Smith, the coach of former 100-meter world-record holder Maurice Greene, euphemistically calls the “Negative Acceleration Phase.”‘ The race may be over in ten seconds, but most sprinters hit their top speed after 50 to 60 meters, sustain it briefly, then start to fade. Usain Bolt’s ability to stride magisterially away from his 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 Jose Luis Gonzalez 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 a mechanistic—almost mathematical—view of human limits: like a car with a brick on its gas pedal, you go until the tank runs out of gas or the radiator boils over, then you stop.

But that’s not the whole picture. With the rise of sophisticated techniques to measure and manipulate the brain, researchers are finally getting a glimpse of what’s happening in our neurons and synapses when we’re pushed to our limits. It turns out that, whether it’s heat or cold, hunger or thirst, or muscles screaming with the supposed poison of “lactic acid,” what matters in many cases is how the brain interprets these distress signals. With new understanding of the brain’s role come new—and sometimes worrisome—opportunities. At its Santa Monica, California, headquarters, Red Bull has experimented with transcranial direct-current stimulation, applying a jolt of electricity through electrodes to the brains of elite triathletes and cyclists, seeking a competitive edge. The British military has funded studies of computer-based brain training protocols to enhance the endurance of its troops, with startling results. And even subliminal messages can help or hurt your endurance: a picture of a smiling face, flashed in 16-millisecond bursts, boosts cycling performance by 12 percent compared to frowning faces.

Over the past decade, I’ve traveled to labs in Europe, South Africa, Australia, and across North America, and spoken to hundreds of scientists, coaches, and athletes who share my obsession with decoding the mysteries of endurance. I started out with the hunch that the brain would play a bigger role than generally acknowledged. That turned out to be true, but not in the simple it’s-all-in-your-head manner of self-help books. Instead, brain and body are fundamentally intertwined, and to understand what defines your limits under any particular set of circumstances, you have to consider them both together. That’s what the scientists described in the following chapters have been doing, and the surprising results of their research suggest to me that, when it comes to pushing our limits, we’re just getting started.


“A voyage to the outer reaches of human capacity.” – David Epstein, author of Range

“Reveals how we can all surpass our perceived physical limits.” – Adam Grant


“Makes the case that we’re actually underestimating our potential, and reveals how we can all surpass our perceived physical limits.” – Adam Grant,

“If you want to gain insight into the mind of great athletes, adventurers, and peak performers then prepare to be enthralled by Alex Hutchinson’s Endure.” – Bear Grylls, Mt. Everest summiteer and host of NBC’s Running Wild with Bear Grylls

“Fascinating (and motivating). … Hutchinson sheds light on how humans accomplish our most absurd athletic achievements.” – Esquire

“A perfect book for the armchair athlete. … If you ever wonder, How do they do that? Hutchinson has the answers. … Discovers that what we think of as our limits are set by our minds, not by our bodies.” – Success (”AHA! Reading List”)

“Alex Hutchinson’s Endure is so much more than a sports book. It is a voyage to the outer reaches of human capacity.” – DAVID EPSTEIN, author of Range and The Sports Gene

“Hutchinson looks at the art and science of endurance, with a focus on running but with take-aways that can be applied to any project, mental or physical.” – Globe and Mail (Toronto)

“[Hutchinson] has a true gift for writing compelling sports stories and combining them with deft analyses of cutting-edge research. … A captivating and often moving book with something to offer readers interested in health, athleticism, neuroscience, and the human condition.” – Kirkus (*starred review*)

“Persuasive and motivating. … Transports readers to a realm where psychology, environment, and physiology all intersect.” — Booklist (*starred review*)

“Want to achieve more? Often that means you have to do more — and Alex will show you how.” – Inc.

“We’re all intrigued by amazing feats of human endurance, from Everest to marathon world records to global Ironman competitions. How do they do it? Alex Hutchinson’s Endure explores the topic from every conceivable angle. An essential read for every endurance athlete.” – AMBY BURFOOT, 1968 Boston Marathon winner, Runner’s World writer-at-large, and editor of Runner’s World Complete Book of Running

“Carefully researched and based on the most current ideas in the science of running, Alex Hutchinson’s Endure is written with a fluency that makes it easily accessible for all runners. This is an excellent resource for anyone seeking to better to understand how our minds influence our ultimate performances.” – TIM NOAKES, emeritus professor of exercise science at the University of Cape Town

“The best popular science book on human performance I’ve ever read.” – Mark Burnley, Ph.D., School of Sport and Exercise Sciences at the University of Kent

“Examines how we can push beyond our limits. … Gives a gripping insight into the mind of great athletes, adventurers and peak performers to find out what gives them the capacity to push harder and achieve more.” – The Independent (Ireland)

“Endure is a pure science book that goes deep, especially into the mind, and the pacing and story-telling are top notch.” – Runner’s World

“Cinematic. … Thrilling. … Hutchinson excels at making the science cohere around his central question: what limits us, our body or our mind?” – Canadian Running

“A fascinating exploration of the limits of the human body—and, to a large extent, the human mind. …. A must-read. … Highly relevant for those looking to better understand and improve their performance off the playing field, too. ” – BRAD STULBERG and STEVE MAGNESS, authors of Peak Performance

“So good. Smart, inspiring, and just fun to read. Makes me wanna be a better runner (and faster reader).” – GRETCHEN REYNOLDS, New York Times “Well” columnist and author of The First 20 Minutes

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