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

Book Link: Amazon (smile)

There's an old Seinfeld line that goes something like "I heard a weatherman say that 75% of your body heat is actually lost through the top of the top of the head. Which sounds like you could go skiing naked if you got a good hat.” (link) and that is similar to what I feel this book is trying to say: The brain controls how and when your body gives up so training the brain has the best impact on performance. In reality, it's much more nuanced than that (obviously) and the author acknowledges as much right at the end:

"If you randomly select a hundred people off the street and have them race a marathon, the finishing order will mostly depend on easily measured physiological parameters like VO₂max. If, on the other hand, you’re comparing a mostly homogeneous group of people, like Olympic marathoners, the physical differences will be much subtler, so the mind will begin to play a role."

For me, this was an incredibly fascinating read through a lot of the science behind what role your brain plays in your overall endurance. It's not the only factor by any means but being able to push through pain is something Navy Seal training has taught for decades and makes a lot of sense. This was easily the most highlighted book I've ever read and some of the lessons and data points will both stick with me and become part of my training. I really like the framing of the book around the Kipchoge Breaking2 effort and how these factors played into the success that day (and later in the INEOS version that broke the 2-hour barrier). Strong recommend for reading this if you are all interested in endurance sports, psychology, efficiency in things (especially the human body), or just interested in understanding how atheletes traing and push and motivate themselves.

Some highlights/thoughts from my reading: 1. In a wide variety of human activity, achievement is not possible without discomfort. 2. 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. 3. 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. 4. To their frustration, physiologists have found that the will to endure can’t be reliably tied to any single physiological variable. 5. 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. 6. 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. 7. 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. 8. 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.” 9. 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. 10. 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. 11. 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. 12. if you understand how a machine works, you can calculate its ultimate limits. 13. VO2max.(Modern scientists call it maximal oxygen uptake, since it’s a measure of how much oxygen your muscles actually use rather than how much you breathe in.) 14. They drew an explicit link between the biochemical “steady state” of athletes like DeMar, who could run at an impressive clip for extended periods of time without obvious signs of fatigue, and the capacity of well-trained workers to put in long hours under stressful conditions without a decline in performance. 15. It was in preparing for this talk that he had his crucial epiphany about the rarity of deaths from exhaustion, like Henry Worsley’s. Whatever our limits are, something must prevent us from exceeding them by too much. And that something, he reasoned, must be the brain. 16. In the final days of the record attempt, Van Deren’s feet were so beat up that she had to start each day by crawling along the trail until, thanks to the familiar numbing of endorphins, she could stand up and start putting weight on them. 17. he began to assemble a coherent picture with two key planks. First, the limits we encounter during exercise aren’t a consequence of failing muscles; they’re imposed in advance by the brain to ensure that we never reach true failure. And second, the brain imposes these limits by controlling how much muscle is recruited at a given effort level 18. I asked Noakes for the single most convincing piece of evidence in favor of his theory, he said, without hesitation, “the end spurt.” How could the runners at Comrades, after pushing themselves through 56 miles of hell, summon a finishing sprint to beat the 12-hour limit? Conventional physiology suggests that you get progressively more fatigued over the course of a run, as muscle fibers fail and fuel stores are emptied. But then, when the end is in sight, you speed up. Clearly your muscles were capable of going faster in the preceding miles; so why didn’t they? “That shows that our ...more 19. “perceived exertion is the single best indicator of the degree of physical strain,” since it integrates information from muscles and joints, the cardiovascular and respiratory systems, and the central nervous system. 20. Perceived exertion—what we’ll refer to in this book as your sense of effort—isn’t just a proxy for what’s going on in the rest of your body, he argued. It’s the final arbiter, the only thing that matters. If the effort feels easy, you can go faster; if it feels too hard, you stop. That may sound obvious, or even tautological, but it’s a profound statement—because, as we’ll discover, there are lots of ways you can alter your sense of effort, and thus your apparent physical limits, without altering what’s happening in your muscles. Case in point: getting mentally fatigued increases your sense of ...more 21. Just like a smile or frown, the words in your head have the power to influence the very feelings they’re supposed to reflect. 22. When Kipchoge tiptoes with exaggerated care onto the treadmill, one of the scientists edges around to the back of the machine, ready to be a spotter if needed. It’s only the second time Kipchoge has run on a treadmill—the first time was during the initial selection process—and it’s hard not to think of Bambi flailing around on the ice. Kipchoge’s lab data, Jones later confides, was surprisingly ordinary, presumably because he was so uncomfortable on the treadmill. 23. top athletes are not immune to pain; they feel it like everyone else. But there were dramatic differences in pain tolerance: the national-team swimmers endured an average of 132 contractions before calling for mercy, compared to 89 in the club swimmers and 70 in the nonathletes. The differences, Gijsbers suggested, must result from the systematic exposure to intense but intermittent pain during training—perhaps by harnessing brain chemicals like endorphins, or perhaps simply thanks to psychological coping mechanisms. “It is reported,” he noted drily, “that pain can be strangely satisfying to ...more 24. simply getting fitter doesn’t magically increase your pain tolerance. How you get fit matters: you have to suffer. 25. pain in training leads to greater tourniquet tolerance, and greater tourniquet tolerance predicts better race performance. 26. 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. 27. One of the most familiar is lactate threshold, the point at which you’re working hard enough that levels of lactate in your blood start creeping inexorably upward. A more recently developed concept is critical power, which is the point beyond which your muscles can no longer stay in the sustainable “steady state” equilibrium fetishized by Harvard Fatigue Laboratory researchers. Sixty minutes of all-out exercise, for a well-trained athlete, sits in the excruciating gap between these two markers, 28. The drug was an early version of crystal methamphetamine, and German military officials took a keen interest in the results. They piloted Pervitin later that year on military drivers deployed in the invasion of Poland, which triggered World War II; convinced of its usefulness, the Nazis distributed it to all branches of the military. Between April and July 1940 alone, more than 35 million tablets of “Panzerschokolade” (tank chocolate) fueled the Blitzkrieg across Europe, spurring lasting rumors of a Nazi superpill that gave soldiers extraordinary powers. (The dark aftereffects of crystal meth ...more 29. his Tor des Géants subjects, who took more than 100 hours, on average, to complete the race, ended up losing just 25 percent of their pre-race leg strength—a result that, on the surface, makes little sense. “Okay,” Millet jokes, “so if I run 200 miles, I’m less fatigued than if I run 100 miles!” This counterintuitive finding, on its own, already hints that leg muscles aren’t what ultimately limit ultra-endurance athletes. 30. At the point of exhaustion in a long endurance challenge, the legs are merely unwilling, not incapable. 31. In hilly mountain races, the microscopic muscle damage inflicted with each stride is magnified by the jarring eccentric muscle contractions as you race downhill (a drama that plays out in miniature in the early downhill miles of the Boston Marathon every April). If your legs aren’t hardened against the rigors of downhill running, your muscles really will limit your speed—but as a result of structural damage, and the associated pain and loss of coordination, rather than ordinary fatigue. 32. Only twice in that time has an 800-meter record been set with a faster second lap, which is the opposite of what is seen in longer races. In fact, the three-second improvement in the record since the 1960s is almost entirely due to runners speeding through a faster first lap; the second lap has stayed nearly constant, suggesting some sort of physiological limit for sprinting on fatigued legs. 33. Another key part of the dive reflex is massive peripheral vasoconstriction: the blood vessels in your arms and legs squeeze nearly shut, sending blood flooding back to your core, where it maintains the crucial oxygen supply to your heart and brain for as long as possible. This shift of blood volume to your torso also helps your lungs resist collapse under the pressure of deep dives, since fluids (unlike air) are nearly incompressible. All it takes to trigger these changes is dunking your face in cool water; in fact, the sensors appear to be primarily around the nose, lending credence to the ...more 34. The spleen mainly acts as a blood filter, but it also holds a reservoir of oxygen-rich red blood cells that can be deployed in emergencies. In seals, the organ is basically a natural scuba tank: it can hold more than twenty liters of red blood cells, and during dives it contracts like a wrung-out sponge, shrinking by 85 percent as it pushes the blood into circulation. 35. “anticipatory regulation”: your brain uses knowledge that is gathered consciously, like an impending dive or a looming finish line, to activate or deactivate safety mechanisms that are otherwise purely unconscious. 36. One of the key researchers on the performance-enhancing effects of oxygen? A guy named Roger Bannister, who published “The Effects on the Respiration and Performance During Exercise of Adding Oxygen to the Inspired Air” in the Journal of Physiology just over two months after breaking the four-minute-mile barrier in 1954. Boosting the air’s oxygen content from the standard 21 percent to 66 percent, he found, allowed him to double his time to exhaustion on a steep uphill treadmill test. 37. In 2008, they adopted a simpler and more practical approach, shipping seven slushie machines to Beijing and deploying them at the venues for track, cycling, soccer, triathlon, and several other sports. Just as the transformation of liquid water to vapor cools your skin when you sweat, the “phase change energy” of ice melting to water in your stomach provides an extra cooling boost beyond what you would get from simply drinking a cold drink. Tests by Australian sports scientists showed that a crushed ice slurry sweetened to the same degree as a sports drink could lower core temperatures by one ...more 38. There’s a reason athletes don ice-filled vests and cooling sleeves and drape ice towels over their necks: these interventions don’t alter your core temperature, but they do influence how hot you feel—and that, in turn, dictates how hard you’re able to push. Further evidence that perception is reality: a British study in 2012 showed that cyclists in a heat chamber went 4 percent faster when the thermometer was rigged to display a falsely low temperature (79 instead of 89 degrees Fahrenheit). 39. In 1990, the average top-100 runner had clocked in at just over 5ʹ8ʺ and 131 pounds; by 2011, those numbers had dropped to under 5ʹ7ʺ and 124 pounds. The reason, the researchers suspected, was simple: the heavier you are, the more heat you generate while running around. 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. 40. When you fail to replace lost fluids, you start craving a drink, and your kidneys begin reabsorbing fluid that would otherwise become urine. If that’s not enough to restore your internal balance, fluid will start draining out of your cells and into your veins and arteries to maintain the necessary volume of blood pumping through your body. These adjustments will buy you some time, but eventually your blood will get so concentrated that your brain will start shrinking as fluid is sucked out by osmosis, tearing delicate cerebral veins and ultimately killing you. 41. 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 ...more 42. the importance of any underlying physiological signal depends in part on how your brain receives and interprets it. “When you drink, you’re also affecting your thirst, your perception, your psychology, your motivation,” 43. thirst and antidiuretic hormone secretion both decreased anyway, presumably in response to the sensation of water flowing down the throat. And when they reversed the experiment, sending the same amount of water down the nasogastric tube instead of letting the subjects swallow it, it was less effective in quenching thirst even though the water was allowed to stay in their stomachs. This, in turn, helps to explain why a later study found that swallowing small mouthfuls of water—too small to make any difference to overall hydration levels—boosted exercise performance by 17 percent compared to ...more 44. 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 ...more 45. high-fat diets don’t just ramp up fat burning; they actually throttle carbohydrate usage by decreasing the activity of a key enzyme called pyruvate dehydrogenase. 46. 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. 47. in 2004, Jeukendrup and his colleagues tried a different approach: this time they asked the cyclists to swish the sports drink in their mouths and then spit it out without swallowing. It worked: simply having the sports drink in your mouth seemed to be more important than getting it into your bloodstream and to your muscles. It’s important to note that these studies were placebo-controlled: the drinks all tasted the same. 48. 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. 49. If you want running at 5:00-mile pace to feel easier, you should head out the door and run at 5:00-mile pace—a lot. Over time, your heart will get stronger, your muscles will grow more energy-producing mitochondria, and you’ll sprout new capillaries to distribute oxygen-rich blood. These changes will allow you to sustain 5:00 pace with less physiological strain, and they’ll also attenuate the distress signals that your muscles and heart send back to the brain. The pace will feel easier, so you’ll be able to sustain it for longer. 50. ultra-runners have a higher pain tolerance than nonathletes, and even over the course of a single year the pain tolerance of athletes waxes and wanes with training cycles. In this sense, all training is brain training, even if it doesn’t specifically target the brain. The struggle to keep going against a mounting desire to stop—that usually limits race speed. 51. 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. Was there a way, he wondered, of training the brains of the former to look more like the latter? 52. He glanced around at the hundreds of thousands of dollars’ worth of machinery arrayed on the infield, the laptops and transmitters, the sensors and wires poking out of his bike shorts. “You can do all this shit, but it all comes down to two guys on a bike, trying to beat each other.” 53. the cyclists rode 1.3 percent faster when they thought they had received a moderate dose, 3.1 percent faster after a high dose, and 1.4 percent slower when they thought they got the placebo. In reality, all the pills were placebos. The performance boost, and associated changes in how much pain or effort they perceived during the rides, were entirely fueled by their own expectations. 54. in one study, she found that simply saying “Here is your ball. So far it has turned out to be a lucky ball.” boosted golf putting performance by 33 percent compared to saying “This is the ball that everyone has used so far.” 55. Rigging the thermometer to display a falsely low temperature counteracts some of the endurance-sapping effects of heat. Using a clock that runs fast or slow, or lying about how much distance an athlete has covered, can help or hurt performance depending on the context. Several studies have used virtual reality systems to allow competitors to race against their own previous performances—a benchmark that, by definition, the subjects are confident they can match. This turns out to be true, even when the virtual rivals are secretly sped up, though only up to a point. Race against a ...more 56. In the end, the most effective limit-changers are still the simplest—so simple that we’ve barely mentioned them. If you want to run faster, it’s hard to improve on the training haiku penned by Mayo Clinic physiologist Michael Joyner, the man whose 1991 journal paper foretold the two-hour-marathon chase: Run a lot of miles Some faster than your race pace Rest once in a while 57. If you randomly select a hundred people off the street and have them race a marathon, the finishing order will mostly depend on easily measured physiological parameters like VO₂max. If, on the other hand, you’re comparing a mostly homogeneous group of people, like Olympic marathoners, the physical differences will be much subtler, so the mind will begin to play a role.