Endure - by Alex Hutchinson
Published:
Endure - by Alex Hutchinson
Read: 2024-08-16
Recommend: 8/10
I better understand why I performed so well in the 2021 Boston Marathon, setting a personal record of 2:46. My strategy included extensive carb loading before and during the race, positive affirmations, consuming three caffeinated gels and seven regular gels totaling 1,000 calories, and hydrating with water or Gatorade at every aid station. The crowd’s cheers helped dull my pain, allowing me to maintain focus on my running without getting distracted by other runners and performers along the course. Additionally, I appreciated the author’s engaging storytelling, which was supported by extensive research.
Notes
Here are some text that I highlighted in the book:
The limits of endurance running, according to physiologists, could be quantified with three parameters: aerobic capacity, also known as VO2max, which is analogous to the size of a car’s engine; running economy, which is an efficiency measure like gas mileage; and lactate threshold, which dictates how much of your engine’s power you can sustain for long periods of time.
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.
One of the most urgent items on the agenda is figuring out exactly what and how much the athletes should drink during the race. Instead of aid tables every five kilometers, as is standard in big-city marathons, the Breaking2 team plans to ride alongside the athletes on a bike—saving, they estimate, about seven seconds per bottle handoff—and distribute drinks every three kilometers or so. The goal is to keep the athletes fueled by providing 60 to 90 grams of carbohydrate per hour, which is far more than the athletes are used to.
Freund isn’t the only one to find that well-trained athletes can tolerate more pain; others have shown that regular physical training, especially if it involves unpleasant high-intensity workouts, increases your pain tolerance.
In 2010, a team of researchers led by Alexis Mauger, who was then at the University of Exeter, in Britain, showed that giving well-trained cyclists 1,500 milligrams of acetaminophen—plain old Tylenol—boosted their performance in a 10-mile time trial by about 2 percent compared to when they were given a placebo. The drugged cyclists were able to push to a higher heart rate and accumulate higher levels of lactate in their blood, while their perceived effort remained the same as during the placebo ride. Less pain made the effort feel easier, allowing the cyclists to push closer to their true physiological limits, the researchers argued.
we don’t just run to the point of failure; we pace ourselves to go as fast as possible while never reaching failure. This process of managing fatigue over a prolonged period of time—enduring the rack rather than submitting to the guillotine—puts a greater emphasis on managing pain.
warm air is less dense and thus offers an aerodynamic advantage, but too much warmth risks overheating the cyclist.
Like a wounded soldier on a battlefield, or a kudu cornered by a hungry lion, athletes in the heat of competition exhibit a phenomenon called “stress-induced analgesia,” which enables them to ignore otherwise debilitating levels of pain.
Some of the most epic tales and Bunyanesque feats in sports involve athletes who defied pain to score the winning point or outlast their opponent: hockey player Bobby Baun’s overtime winner for the Toronto Maple Leafs in the 1964 Stanley Cup Finals, skating on an ankle he had fractured earlier in the game; Willis Reed taking on Wilt Chamberlain in the 1970 NBA Finals with a torn thigh muscle; Kerri Strug’s gold-medal-clinching vault on a sprained ankle at the 1996 Olympics. In fact, playing through a broken limb isn’t even that rare, even when the stakes are lower: Philadelphia Eagles quarterback Donovan McNabb had the best passing game of his career on a broken ankle in 2002; Boston Bruins center Gregory Campbell played out a shorthanded shift after a slap shot broke his fibula during the 2013 playoffs; Denver Broncos safety David Bruton Jr. played another ninety-five snaps on a broken fibula after a first-quarter collision in 2015.
As a result, starting with observations of wounded soldiers during the U.S. Civil War, doctors and pain researchers have concluded that pain is fundamentally a subjective, situation-dependent phenomenon. For example, stress, fear, and anxiety activate an impressive array of brain chemicals, including endorphins (the body’s store-brand opioid drugs) and endocannabinoids (the body’s cannabis), to dull or completely block pain that would overwhelm you in other circumstances. In evolutionary terms, pain may serve a valuable function by telling you to stop and allow an injury to heal. “But if you’re a deer being chased by a wolf and you trip and break a leg,” says Mogil, the McGill pain researcher, “you need to forget about that pain until later.”
pain, in most contexts, is a warning light on the dashboard. It instructs you (sometimes very insistently) to slow down, and in most contexts you heed that warning without even realizing you’re doing it. But it’s not an absolute limit.
Top athletes, far from being immune to lactate, are actually able to recycle it into fuel more efficiently than lesser athletes.
The summit of Everest, scientists had determined, would offer barely a third as much oxygen as at sea level.
For every 100 calories of food you eat, in others words, you might get 25 calories of useful work and 75 calories of heat. As wasteful as that sounds, it’s surprisingly similar to the efficiency of a typical internal combustion engine.
Earlier studies with goats and dogs whose brains were cooled by irrigating cold water through their noses had suggested that brain temperature, rather than core temperature (which is typically measured rectally), is what determines your ultimate thermal limits. If a slushie cools your brain, then your brain lets you keep pedaling a little longer even as the rest of your body heats up beyond its usual limits. A related possibility is that you have temperature sensors in your stomach itself, where the slushie melts.
Tall people also have more skin surface area, which allows them to shed more heat by sweating—but the extra weight swamps the effects of the extra skin, putting bigger and taller runners at a subtle disadvantage.
Then half the cyclists received two weeks of training in “motivational self-talk” specifically tailored to exercising in heat, which basically involved suppressing negative thoughts like “It’s so hot in here” or “I’m boiling,” and replacing them with motivational statements like “Keep pushing, you’re doing well.” The self-talk group improved their performance on one of the endurance tests from 8 minutes to 11 minutes—and in doing so, pushed their core temperatures at exhaustion more than half a degree higher. “We’re now pretty sure it’s not just a physical thing,” Cheung says of the critical temperature concept. “There seems to be a strong mental-psychological component to it.” The right frame of mind, in other words, allows you to push beyond your usual temperature limits: “Even if you’re already fit, you can still improve your perception of heat and how you perform in it.”
the fastest finishers tend to be the most dehydrated. For example, among 643 finishers in the 2009 Mont Saint-Michel Marathon in France, sub-three-hour finishers averaged a loss of 3.1 percent of their starting weight; finishers between three and four hours averaged 2.5 percent; and those clocking more than four hours were the only ones to obey the 2 percent rule, losing on average 1.8 percent. The results don’t prove that drinking makes you slower, but they certainly raise further questions about the claim that any loss greater than 2 percent slows you down.
The chemical reactions involved in burning fat and carbohydrate produce two key by-products: carbon dioxide, which you breathe out, and water—which actually adds to the amount of fluid available in your body. Even more significant, your body stores carbohydrate in your muscles in a form that locks away about three grams of water for every gram of carbohydrate. This water isn’t available to contribute to essential cellular processes until you start unlocking the carbohydrate stores, so your body sees it as “new” water when it’s released during exercise. For decades, these factors were assumed to be insignificantly small. But in 2007, British scientists at the University of Loughborough estimated that a marathoner could conceivably lose 1 to 3 percent of his or her body mass without any net loss of water.
In the first trial, they drank as much as they wanted; in the other five, they were assigned varying levels of hydration ranging from nothing to enough to fully replace all their sweat losses. Sure enough, being hydrated improved performance: in the three trials where the cyclists were forced to drink less than they’d chosen to in the first trial, they were slower than the three higher-hydration trials. But there was no further improvement when they drank more than they had chosen to in the first trial. Avoiding thirst, rather than avoiding dehydration, seems to be the most important key to performance.
swallowing small mouthfuls of water—too small to make any difference to overall hydration levels—boosted exercise performance by 17 percent compared to rinsing the same amount of water in the mouth and then spitting it out. When it comes to quenching your thirst, perception—not just in your mouth, but in the cool flow of liquid down a parched throat—is, at least in part, reality.
In later—and more successful—marathons, he followed a carefully planned hydration strategy. During his 2007 world-record race in Berlin, according to Stellingwerff, Gebrselassie’s plan involved a bottle of sports drink three hours before the race, another one an hour before the race, and then a total of two liters of water and sports drink during the race, consumed at 5K intervals. He wasn’t following the 2 percent rule, but he was certainly following a premeditated drinking plan. One final caveat is that our ability to tolerate temporary bouts of dehydration is, well, temporary. Marathoners can handle 10 percent dehydration for a few hours. But that assumes you’re properly hydrated when you arrive at the start line—a factor that is, if anything, even more important than what you drink during exercise, according to Stephen Cheung’s research.
To me, the primary message is that, like oxygen and heat and (as we’ll discover) fuel, the loss of fluids first makes itself felt via the brain. Thirst, not dehydration, increases your sense of perceived effort and in turn causes you to slow down. Eventually, the physiological consequences of dehydration assert themselves, increasing the strain on your cardiovascular system and pushing your core temperature up as the volume of blood in your arteries decreases. But that only happens if you’ve already ignored the signs of thirst. That means that hydration still matters.
not that you shouldn’t drink when you have the chance, but that you shouldn’t obsess about it when you don’t. “It’s one less psychological crutch,” he says, “to hold you back from a top performance.”
But elite racewalkers are . . . different. The event, which requires walking as quickly as possible while straightening your leg with each stride and keeping one foot on the ground at all times, is often the butt of jokes, both for its distinctive swivel-hipped stride and for its fundamental premise: NBC sports commentator Bob Costas famously compared it to a contest to see who can whisper the loudest.
no matter how fit you are you’ll burn the same fat-carb mix at any given relative intensity. Eating a diet high in either fat or carbohydrate also tilts your preferred fuel mix in that direction. But even taking these factors into account, carbohydrates dominate for any intense exercise: one study found that over the marathon distance, running at 2:45 pace relied on 97 percent carbohydrate fuel, while slowing down to 3:45 pace reduced the carbohydrate mix to 68 percent.
Subsequent biopsy studies confirmed that the amount of glycogen you can stuff into your muscles is a pretty good predictor of how long you’ll last on a treadmill or stationary bike test to exhaustion. There are other sources of carbohydrate in the body; your liver, for example, can store 400 or 500 calories of glycogen for use throughout the body, compared to about 2,000 for fully loaded leg muscles. (That’s why it’s useful to eat a small breakfast a few hours before a morning marathon: while your muscles remain fully stocked, your liver glycogen gets depleted because it fuels your energy-hungry brain while you sleep.)
If that’s the case, then it makes sense for endurance athletes to stock up on carbohydrates as much as possible. And that, more or less, is what sports nutritionists have been advocating since the 1970s. Keep your glycogen levels high by consuming a diet that gets 60 to 65 percent of its calories from carbohydrate; top up your stores by carbo-loading in the final few days before a competition; and in events lasting longer than about ninety minutes, eat or drink some easily digested carbohydrates to supplement your stored glycogen, which will otherwise run out.
One study found that Kenyan runners, who currently hold 60 of the top 100 men’s marathon times in history, typically get 76.5 percent of their calories from carbohydrate, including 23 percent from ugali, a sticky and stomach-filling cornmeal mash, and 20 percent from the copious spoonfuls of sugar they heap into their tea and porridge. Another 35 times on the top-100 list are held by Ethiopians; a similar study found that they get 64.3 percent of their calories from carbohydrate, with the biggest contribution from injera, a sourdough flatbread made from a local grain called teff. If there’s an alternative diet plan that’s better for endurance performance, no one has told the best endurance athletes in the world.
I described the hydration plan that Haile Gebrselassie used when he set a world record of 2:04:26 at the Berlin Marathon in 2007, which involved drinking about two liters of fluid during the race. In practice, his plan was as much focused on fueling as on hydration. Of the two liters of fluid he planned to consume during the race, 1.25 L was sports drink (the rest was water), and he also took five sports gels, providing a total of between 60 and 80 grams of carbohydrate per hour. That number is significant, because scientists have traditionally figured that 60 grams an hour (about 250 calories) is pretty much the maximum amount you can absorb during exercise. The rate-limiting step is the absorption of carbohydrate from the intestine into the bloodstream. But Gebrselassie was taking advantage of newly published (at the time) data showing that if you combine two different types of carbohydrate—glucose and fructose, for example—they pass through the intestinal wall using two different cellular routes that can operate simultaneously, enabling you to absorb as much as 90 grams of carbohydrate per hour.
For the rest of us, glucose-fructose mixes are now incorporated in standard sports drinks from companies like PowerBar and Gatorade. If you can stomach more than 60 grams per hour, the higher absorption rate should help stave off the depletion of your glycogen stores and allow you to maintain a faster pace for longer without hitting the wall.
brain areas associated with reward were lighting up as soon as the subjects had carbohydrate in their mouth. Crucially, neither the brain scan nor cycling performance showed any effects when the drink was artificially sweetened, but the benefits returned when maltodextrine, a tasteless and undetectable carbohydrate, was added to the artificially sweetened drink. The sweet taste of sugar, in other words, is not enough to trigger the benefits. Instead, the mouth appears to contain previously unknown (and as yet unidentified) sensors that relay the presence of carbohydrate directly to the brain. In Tim Noakes’s central governor framework, it’s as if the brain relaxes its safety margin when it knows (or is tricked into believing) that more fuel is on the way.
In practice, these findings mean that the benefits of sports drinks and other mid-race carbohydrates for short bouts of exercise are irrelevant as long as you don’t start out with an empty stomach and depleted fuel stores. (Pro tip: you shouldn’t.) On a more theoretical level, the results are among the strongest evidence we have that your brain is looking out for your well-being in ways that are outside your conscious control and that kick in long before you reach a point of actual physiological crisis.
To see just how much of a difference high-fat diets could make, a team led by Jeff Volek of Ohio State University (and including LCHF pioneer Stephen Phinney) recruited twenty elite ultra-runners and Ironman triathletes, half of whom had voluntarily switched to an LCHF diet months or years earlier, and brought them to the lab for testing. The results, published in the journal Metabolism in 2016, showed that the fat-adapted runners were able to burn fat twice as quickly as the non-fat-adapted control group. During a three-hour treadmill run at a moderate pace, they relied on fat for 88 percent of their energy, compared to 56 percent for those following a standard carbohydrate-heavy diet. That last number is worth noting: even on a high-carbohydrate diet, you still have access to your fat stores during exercise.
Olympic triathlon medalist Simon Whitfield, for example, turns out be about 50 percent carbohydrate, 30 percent protein, and just 20 percent fat—not exactly skim milk and egg whites, but still closer to standard sports nutrition guidelines than to LCHF territory. And Tour de France cyclist Dave Zabriskie, when I contacted him to ask about his LCHF experience, said that the experiment was interesting but hardly performance-enhancing: “For long easy training, it’s good. For day-after-day racing like the Tour, you have to eat the carbs.”
he helped me devise a twelve-week routine, five days a week, rotating through three different cognitive tasks (arrows, shapes, letters), starting with extremely modest sessions of fifteen minutes and progressing, if all went well, to an hour and a half. By triggering the flood of neurotransmitters associated with mental fatigue and, in particular, response inhibition over and over, we hoped that my brain would adapt to the insult—and that my resistance to mental fatigue would translate into an ability to sustain a slightly faster pace at the same effort.
Being boring is an important characteristic for inducing mental fatigue and, therefore, a brain training effect
For one thing, brain endurance training is mind-numbingly boring; for another, it’s incredibly time-consuming. For anyone whose athletic pursuits have to fit around family and job obligations, making time for marathon training is already tough enough. Adding in another hour or more a day is a big ask, especially when the benefits remain unproven. That’s why Marcora’s most recent studies have used a combined protocol where subjects do physical and mental training at the same time. In 2015, Staiano and Marcora presented recently declassified results from a military-funded study of thirty-five volunteers who had trained three times a week for an hour at a time on stationary bikes. Half of the volunteers did brain training while cycling, using the flashing-letters test that I had tried. After twelve weeks, the physical-training-only group had improved their time to exhaustion by 42 percent; in comparison the physical-plus-brain-training group had improved by a whopping 126 percent. This hybrid protocol is more time-efficient and less boring than the brain-training-only protocol I followed—and with effects that large, I suspect lots of people would be willing to endure a little boredom.
A major strand of his research has focused on the role of interoception—the brain’s monitoring of internal signals in the body like temperature, hunger, blood-oxygen levels, and so on—in anxiety disorders and addiction. Anxious people, he found, tend to overreact to negative stimuli, producing a distinct pattern of brain activity. Elite endurance, athletes, on the other hand, display a completely opposite response pattern.
Of course, the power of belief has often been oversold, like the self-help books that claim sub-four-minute miles became easy as soon as Roger Bannister showed it was possible. In any honest accounting, training is the cake and belief is the icing—but sometimes that thin smear of frosting makes all the difference.
what has captivated me about the new wave of brain-centered endurance research isn’t really its performance-boosting potential. For millions of people around the world, endurance challenges are somewhere between a hobby and an addiction, a form of grueling self-test that has no particular health justification. Why? If races were really just plumbing contests—tests of whose pipes could deliver the most oxygen and pump the most blood—they would be boringly deterministic. You race once, and you know your limits. But that’s not how it works.
I tried to explain to her that every good race involved exceeding what felt like my physical limits. If I ran 800 meters as hard as I could in practice, I might run 2:10; in a race, I might run 1:55. Accessing that hidden reserve was anything but a foregone conclusion, and waiting to see how deep I would manage to dig was what made racing both exhilarating and terrifying.
I’m eager to learn more, in the coming years, about which signals the brain responds to, how those signals are processed, and—yes—whether they can be altered. But it’s enough, for now, to know that when the moment of truth comes, science has confirmed what athletes have always believed: that there’s more in there—if you’re willing to believe it.