What it takes to be a great endurance athlete - Endure, by Alex Hutchinson
Inquiries into peak athletic performance
TLDR - SUMMARY AND INTERVENTIONS
Although Alex Hutchinson’s Endure is a delightful book coming from just the right author, I’m here to save you time. So if you’re results focused, here’s the TLDR takeaways front and center, and the longer review is further below if you’re interested.
One other note, nearly all sports science studies are of laughable quality. You almost always have tiny “N,” participants range from random people off the street to college students, college athletes, amateur athletes, or national-or-higher elite athletes, RCT’s are not as prevalent as you’d hope, statistical tests aren’t used with much sophistication, multiple comparisons are rarely corrected for properly, it’s a congerie of slapstick errors and jumping to out-of-distribution conclusions.
Nevertheless - because studies and individual physiology and performance varies so much, the most we can do is point to things that work for some people some of the time, so that you can try them yourself. So in that spirit, I continue.
Broadly, if you want your endurance performance to be better, the three biggest factors that matter are:
VO2max
You know you’re limited by your VO2max if your muscles and body feel like they have more to give, but you’re breathing hard. Another example would be how it feels to train at altitude - even elite athletes gas out with low lactate levels at altitude. Mostly innate, but 10-30% improvable with endurance training and HIIT.
Lactate threshold
If you’re not breathing that hard, but your legs are heavy and slow or giving out before your breathing, you’ve got a lactate problem. Same as VO2max - partly improvable with endurance training and HIIT, and/or higher pain thresholds.
Mechanical efficiency
Allows you to reduce the costs of movement to give you more headroom on both VO2max and lactate threshhold. As Dan Lieberman tells us in Exercised, one thing a lot of Western athletes don’t do is explicitly model and imitate top performers in their fields. But it’s very common in Kenyans and Ethiopians and other successful non-Western distance runners to explicitly model the cadence, stride, “kick,” and posture of the best runners in their groups to get good at running, and it’s probably a good idea to do the same, whatever your sport.
If you’re at the point that you think you have the above 3 factors dialed in, your performance per-race is likely being limited by one of the following factors:
Pain - the biggest factor when you lump “perceived effort,” the struggle to continue against a mounting desire to stop, in with it. Mostly mental as defined here, because muscle is separated out.
Do HIIT - it not only helps pain tolerance, but also race day performance.1
Avoid or control frowns, tight lips, and tight body language2
Smiling faces and positive self talk probably help3
Caffeine - Supported by multiple studies, they have caffeine energy gels now, too. I mean, caffeine works by blocking adenosine binding in the brain, which makes you tired. What CAUSES that buildup of adenosine? Your ATP furnaces churning away and liberating their phosphates, first giving you one and turning to ADP, then giving you the last phosphate and becoming just A - adenosine.4
Discipline - aka response inhibition. Elite athletes do better on Stroop tests. There’s evidence that even things like interventions around using your non-dominant hand, sticking to a budget, and posture regulation also improve performance, likely by improving “discipline,” which mitigates mental fatigue.5
Tylenol boosts endurance performance without any effect on the muscles, heart, or breathing.
There’s always embracing it - a la Tour de France cyclist Jens Voigt’s famous “Shut up, legs!!”6
Muscle - endurance efforts attenuate muscle output by 10-45%,7 and it’s easy to hit muscular limits8 with more hills or elevation changes than you’re used to. That said, you generally only ever hit muscular limits in short sprints, and in endurance events, it’s typically not the limiting factor.
Do HIIT - it improves muscular strength and capacity.
Running will take more of a damage toll on muscles than biking, swimming, or skiing (likely why running is last in the triathlon), but you can also use this to inform your own training - your legs won’t be at 100% muscular capacity after a run.
Pay attention to the elevation changes and terrain in any upcoming race, and make sure you’re training appropriate amounts of both uphill and downhill to match
Drugs - one of the reliably strongest interventions, twice as strong as injecting pure adrenaline or firing a gun right before a muscle contraction, is amphetamines.9 The Germans found that Pervitin (basically crystal meth) tripled performance on endurance bike rides.10 Harking back to Tylenol, you can use Tylenol, sure. But before drug testing, many Tour de France teams used strong opiates during their performances as well, with sometimes disastrous results.11 But I know if you’re anything like me, you’re asking “sure, sometimes it was disastrous, but did it help them WIN?”12
Oxygen - you need oxygen to fuel the metabolic chains that use carbs and fat to release energy into your bloodstream. This cashes out to VO2max, mostly - but VO2max gets better with training.
Heat - there’s a “critical temperature” of around 104-104.5 F core temp, at which point your body+brain combo will either make you stop or greatly reduce output.
Exercise in heat to promote adaptation. 60-90 minutes of moderate exercise in high heat conditions per day produces changes in a day or two, and full adaptation in about 2 weeks.
Drink “crushed ice slurries,” more popularly known as slushees or slurpees. Not only does drinking it have psychological cooling effects, the ice→water phase transition can lower core temps by as much as 1 degree F, and there may be additional benefits from face / sinus cooling.15
Cool yourself before a race or performance - soaking in cool or cold water beforehand lowers core temperature and allows greater power output.
Positive self talk specifically around heat management and capabilities allowed an improvement of 8-11 minutes in time to exhaustion and core temps a half a degree higher.16
As always, amphetamines, but they are risky in this context. They allow you to push your core temperature higher, without feeling hotter. This can runaway into heat stroke and even death, so be careful.17
Thirst - don’t worry as much about losing weight over the course of your race. Plasma osmolarity is the important thing, and as long as you drink when you’re thirsty, you’ll mostly be fine.18
Swishing and spitting sports drink still gives a boost even if you’re too full for more or not thirsty.19
Fuel - Carb loading good. We all use some mix of carbs and fats while training or racing. You can get more efficient at the “fat” metabolization part of it, and that can have some benefits.
The roughly 60g absorbable per hour while racing can be bumped to 90 for some people if you combine two types of sugar (fructose and glucose, for example)
There’s some signs you should train fasted occasionally to upregulate fat metabolism capabilities, which can go from ~50% ish to 80-90%20
Other - there’s some other stuff that doesn’t fit cleanly into the main 5 categories. tDCS, mental fatigue, reverse VO2max benchmarking, and more.
Now, the full review. We fade in…
Eliud Kipchoge, the best living marathoner in the world, is trying to break the two hour marathon. A team of Nike scientists has worked for years to optimize the attempt and give him his best chance. He has freshly engineered shoes that are 4% more efficient than anything else that exists, a pace car, pace runners that he’s drafting to minimize wind resistance, and more. This is the outermost edge of human capability, and Kipchoge is trying to reach into that numinous, pain and struggle filled cloud of “human possibility” and claw back a sub two hour marathon, and doing it decades before predictions thought it would happen.
He doesn’t succeed in 2017 (the attempt the book relates) - but he *does* succeed in the second 2019 attempt. And although he’s never broken 2:01 in real world marathons (he did set the world record), in 2023 Kelvin Kiptum runs the Chicago marathon in real world conditions in 2:00:35, breaking Kipchoge’s world record.24
Already half-fallen, the two hour marathon is one of a long list of athletic firsts and records that have been steadily whittled away as we have come to understand human physiology, psychology, and limits more comprehensively.
Alex Hutchinson’s Endure is about those limits and that understanding.
Back to the 2 hour marathon - the limits of endurance running can be defined by three parameters. Aerobic capacity (V02 max), running economy (how efficient your gait is), and lactate threshold (how long you can sustain at what output level). Most elite runners that are measured have good scores on two of these, and an outstanding score on one. Medical resident and runner Michael Joyner calculated in 1991 that a runner who was outstanding on all three would be able to complete a marathon in 1:57:58.
The record at the time was 2:06:50 - vastly above. Joyner’s figure was preposterous. But much like Roger Bannister breaking the 4 minute mile barrier led to at least 5 people breaking it within the next year or two,25 putting the number out there creates a new Schelling point. The record was steadily whittled down over the next 30+ years, until we’ve reached Eliud Kipchoge’s recent attempts.
Why does defeating a threshold barrier result in a flood of people also conquering it?
All who break such a barrier soon after must have been right at that barrier in terms of capacity. Why couldn’t they get that extra push, those extra ergs of effort, until they knew?
As Hutchinson himself puts 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.”
Endurance is as much mental as it is physical. Hutchinsons’s favorite definition - credited to researcher Samuele Marcora - is that endurance “is the struggle to continue against a mounting desire to stop.”
Any task lasting longer than a dozen or so seconds requires decisions, whether conscious or unconscious, on how hard to push and when.
It was found by I. Halperin that even powerlifters feel this - “max” attempts are paced according to how many reps you think you’ll do, and what you’re planning to do after the max attempt.26
And how we pace ourselves is intrinsically mental and physical - you judge your pace based on how you feel, how you expected to feel, objective measures like your splits, and by whatever overarching goals or thresholds you have in your head.
But knowing or believing that your ultimate limits are “all in your head” doesn’t make them any less real when you’re pushing yourself at your limits.
Hutchinson is definitely the right person to be writing this book. An Olympic qualifier for the 1500, and a sports and athletics journalist for more than a decade after that, he’s “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.”
“But PB,” you may be thinking, “wouldn’t a scientist or rationalist be better than a journalist?” You might say this, suspecting that most sports medicine studies are absolute dogshit. You almost always have tiny “N,” participants range from random people off the street to college students to college athletes to amateur athletes to national or higher elite athletes. RCT’s are not as prevalent as you’d hope, statistical tests aren’t used with much sophistication, multiple comparisons aren’t corrected for, and it’s a congerie of slapstick errors and jumping to out-of-distribution conclusions.
As Louise M. Burke, the head of sports nutrition at the Australian Institute of Sport, puts it:
“Studies of…endurance performance are sparse and heterogeneous in terms of athlete calibre, duration of adaptation and types of exercise protocol.”
Or as Hutchinson himself puts it:
“They’re…based on well-researched concepts, but the road from theory to practice is littered with the smoking remains of countless heavily hyped ideas that didn’t pan out.”
But precisely because of the study quality and the “smoking remains” of ideas that didn’t pan out, it’s more valuable to have an actual athlete talking to these athletes, coaches, and scientists, because coaches and athletes like Hutchinson have tried to put a lot of these things into practice. So the best quality filter is usually “what elite athletes try and see working in other elites” and “what elite coaches recommend.”
You’d hope for a little better, especially given this is one of those domains that A) people actually care a lot about, because elite athletic performance is a matter of national pride and/or millions of dollars, and B) there’s thousands of researchers, scientists, coaches, and athletes all dedicating serious amounts of energy and time to improving results by <1%. But the limits of human capability are definitionally *the limits.* It’s a genuinely hard problem, and maybe this is the best we can hope for.
Actually, one of my favorite parts about the book is that so many of the people he talks to are such extremely high-human-capital people. They’re ultramarathoners AND doctors AND scientists. They’re former Olympians or Olympic qualifiers who decided to become doctors or researchers and go into sports medicine. Nearly all of them run or practice some athletic discipline fairly seriously on the side, whether it by cyclocross, triathlon, or ultra-endurance events. They’re the creme de la creme, those who are both physically and mentally gifted, the type of person you hope your kids grow up to be.
And what he’s found by talking to all these athletic savants is that brain and body are fundamentally intertwined, and limits under any particular set of circumstances are defined by various borders and tradeoffs between them.
Body as machine.
Endurance initially began being studied as “fatigue” and “physicochemical balance” by places like the British Industrial Fatigue Research Board and Harvards Fatigue Laboratory in the basement of the business school.
By studying miners working at 20k feet, workers building the Hoover dam, Boston marathon winners, and the effects of “heat, humidity, dehydration, starvation, altitude, and other stressors” on soldiers performance in WWII, a view of the human body as a machine that runs on chemicals with the potential for chemical shortages and defined limits began to be built up.
“The machinery of the body is all of a chemical or physical kind. It will all be expressed some day in physical and chemical terms,”
A.V. Hill - Physiologist, 4:45 mile runner, and winner of 1922 Nobel Prize in Physiology or Medicine for his elucidation of the production of heat and mechanical work in muscles.
At the university of Minnesota’s Laboratory for Physical Hygiene, conscientious objectors were tested in the Minnesota starvation experiment, which became the birthplace of relying on the “inclined treadmill” test protocol for V02max measurement - created in this particular study as a protocol that would measure max effort even under starvation conditions.
Scientists gradually fine-tuned their models of endurance by incorporating other physiological traits like economy and “fractional utilization” along with VO2max—the equivalent of considering a car’s fuel economy and the size of its gas tank in addition to its raw horsepower.
It was in this context, of the body as a physical machine, that Michael Joyner proposed his now-famous 1991 thought experiment on the fastest possible marathon.
But the body is more than a machine, and race results at their peak are about much more than just what your V02max is capable of.
“What is really interesting about exercise is not that people die of, say, heatstroke; or when people are climbing Everest, it’s not that one or two die. The fact is, the majority don’t die—and that is much more interesting.”
Tim Noakes - Ultramarathoner, Physiologist and highly lauded researcher
Tim Noakes, a South African physician, scientist, and ultramarathoner himself, has a famous example that he likes to use - in the 1996 Olympic Marathon, Josia Thugwane, the gold medal winner, outsprinted silver medalist Lee Bong-Ju by just 3 seconds. “Do you notice he’s not dead?” he’d say, pointing at Lee. “What does that tell you? It means he could have run faster.”
Noakes posits the idea of a central governor - the idea that the brain regulates and governs your athletic output based on a number of factors, with your raw physical capabilities only one factor in that equation.
Hutchinson points out that this is a controversial idea, and has been controversial for more than two decades, although it’s difficult to see why, when something shaped very much like it MUST be true.
What does Noakes point to as evidence for the central governor? A number of things:
Athletes exercising to exhaustion at high altitudes have puzzlingly low lactate levels when they give up.
Athletes can get an instant performance boost by swishing a carbohydrate drink in their mouth, then spitting it out.
Many world records have been set despite supposedly crippling levels of dehydration or injury.
Tylenol boosts endurance performance without any effect on the muscles, heart, or breathing.
Marathon “anchor times” - if you look at a graph of marathon finish times, there’s always big spurts of people who put in the extra effort to finish right at a given hour or half hour mark27
But most of all, he points to the “end spurt,” the fact that distance athletes the world over speed up on their last laps. If you aggregate the world record lap times in the mile, 5k and 10k, there is a characteristic u-shaped performance curve:
That little uptick at the end of the graph? That’s elite athletes making world record passes, the finest runners in history on the best day of their lives, having a lot of reserve in the tank as they head into their last lap.
But if you’d asked if they were giving 100% effort on every previous lap? These are literally the creme de la creme tackling (and breaking) a world record - of *course* they were giving 100%!
The brain is fundamentally intertwined with the body when it comes to athletic performance.
So what are the factors that most affect the brain’s performance?
Hutchinson breaks down 5 factors and uses a chapter each to talk about them.
Pain
Muscle
Oxygen
Heat
Thirst
Fuel
Let’s talk about pain.
I’m sure most people reading this knows the sensation of going out, getting into the “pain cave” range of exertion, and just turning your brain off for the next hour or two as you push yourself through a twilight realm of not-explicitly-conscious-but-constant suffering.
The fact that pain is a big part of training and athletic performance is going to surprise nobody.
Look at Dianne van Deren. She does ultramarathons, she pulled a sled 430 miles to win the Yukon Arctic Ultra (an event no other female athlete finished), scaled the 22k Aconcagua mountain for a Mayo Clinic research project, set a record for the Mountains-to-the-Sea trail (22 days, 5 hours, 3 minutes) and much more.
Two interesting facts about her: she didn’t even start her ultra-endurance racing career until she was 37, a very late start for an elite athlete. And second, she only started after having a surgery that removed a golf-ball sized section of her temporal cortex.
That surgery affected her sense of direction, her short term memory, and her sense of time - when van Deren races, she has no idea how long she’s been racing. She could be on day 10, and you could tell her it was day 2. She lives in an infinite, unmoving pain cave when she races, with no past and no future. The last couple of days of the Mountain to Sea trail run, van Deren’s feet were in such poor shape, she had to start each day literally crawling until enough endorphins kicked in for her to stand up and start running again - and she still set the record.
Okay, but what does this have to do with me, an athlete with an intact brain?
Scientists like to test pain tolerance by having people dunk their hands in ice water. Most people manage 60-90 seconds before they can’t stand it any more and yank their hands out at 10/10 pain.
In one particular test looking at ultra-endurance athletes, non-athlete controls managed 96 seconds, while 11 TransEurope Footrace28 athletes tested held their hands in the water for the entire 3 minutes the scientists asked for, and rated the pain at about 6/10 afterwards.
Pain threshold is roughly similar across elite and amateur and non-athletes, as measured by cutting off circulation with a blood pressure cuff, then having people clench their fists once a second. All three groups said pain cut in at about 50 contractions. But pain *tolerance* is where athletes come into their own. Non-athletes got to 70 contractions, amateurs to 89, and elites to 132 on average.
Tellingly, when the elite athletes were retested, they scored highest in June during their peak racing season, and lowest in October, their off season, and somewhere in the middle during their regular training period in March. Pain tolerance is at least partly learned and conditioned, and it varies based on your training.
What can you do about pain?
Pain is at least partly psychological, of course. To that end, various interventions that have had positive effects on performance that touch on it include:
Avoid or control frowns, tight lips, and tight body language
Smiling faces and positive self talk probably help
Caffeine
Discipline - aka response inhibition. Elite athletes do better on Stroop tests. There’s evidence that even things like interventions around using your non-dominant hand, sticking to a budget, and posture regulation also improve performance, likely by improving “discipline,” which mitigates mental fatigue.
Tylenol boosts endurance performance without any effect on the muscles, heart, or breathing.
There’s always embracing it - a la Tour de France cyclist Jens Voigt’s famous “Shut up, legs!!”
Finally, adding to the approximately one hundred other reasons, do HIIT. In a study contrasting HIIT and moderate-intensity fitness interventions in non-trained adults over six weeks, fitness, V02max, and lactate threshold increase by roughly the same amount in both groups. But the HIIT group had a 41% increase in pain tolerance, too. AND the HIIT group lasted 148% longer in race conditions, compared to a mere 38% improvement from the moderate-intensity group.29
Probably one of the most interesting results discussed in the book is that some pain is necessary for performance - a series of studies by Markus Amann in 2009 injected fentanyl into the spines of the trained study participants, blocking pain signals from the legs reaching the brain, then asked them to ride 5k as hard as they could. They rode themselves “into a smoking ruin,” by the end many couldn’t get off the bikes by themselves, or even unclip their feet, and not a single one was able to walk. But their times? No faster than when they received placebo injections. The lack of pain had ruined their pacing, and they started fast, pedaled to true muscle exhaustion, then slowed down as their leg muscles no longer responded to their brain signals.
Which brings us to the next limit - muscles.
What muscles are capable of and how close you can come to muscle failure is obviously a part of the limits of athletic performance.
Interestingly, this is less an issue than you might think. Studies with electrical stimulation and simple muscle contractions show that voluntary signals generally get 100% contraction effort from the muscles - there’s no real headroom or safety margin built in.
But athletic competition is about more than simple muscle contractions - it’s about engaging complex chains of muscles, in precise and often in-the-moment adaptive ways.
What can we access from our muscles in those conditions?
Vladimir Zatsiorsky, a biomechanics expert who spent three decades at the Central Institute of Physical Culture in Moscow, the hub of scientific research for the Soviet sport system, before moving to Penn State in the early 1990s, reports that most of us can summon about 65 percent of our theoretical maximum strength. Elite weightlifters can do better, hefting more than 80 percent of their maximum in workouts—and with the psychological boost of a big competition, they can lift, according to one of Zatsiorsky’s studies, an additional 12.5 percent compared to their training best.
Nobody knows how those “training best” maximal numbers were reached.30 To his credit, Hutchinson tried to figure it out - he actually tracked down Zatsiorsky and asked him.
“Unfortunately,” he told me in an email, “I do not remember who mentioned these facts first.”
That doesn’t automatically mean they’re wrong—after all, one of the reasons they crop up in so many “scientific explanations” of superhuman strength is that they sound plausible. But plausibility isn’t the same as proof.”
An interesting fact about muscle pain and function - take lactate, protons, and ATP. If you inject any two of them into a muscle, there’s basically no effect on feeling or capability. This is true even though lactate + protons makes lactic acid. But if you inject all 3? At small amounts, it makes the muscle feel dull or heavy, at large amounts “achy” or “hot,” and more difficult to move. This trio is what makes you feel fatigued, and it requires the full trio.
If you look three hours in at runners versus skiers or bikers, the runners have an 8% decline in voluntary activation of muscle, and the difference is that impact forces cause microscopic damange in the muscles of your legs. But even over ultra-endurance distances, these losses top out at about 10-45% of the muscle’s force producing capacity.
Samuele Marcora did a study where participants cycle at 240 watts until they could no longer continue, then asked them to produce a final 5 second sprint after they had finished - they managed to generate an average 731 watts in that sprint. As Hutchinson puts it “At the point of exhaustion in a long endurance challenge, the legs are merely unwilling, not incapable.”
Broadly, you can reach true muscular limits in short all-out sprints of less than a minute, but for endurance races, muscular limits are less the limiting factor than mental and combined mental / physical factors.
Oxygen
Roger Bannister, of “4 minute mile” fame, published a paper 2 months after he broke 4 minutes in the Journal of Physiology - boosting oxygen content from 21% to 66% allowed him to double his time to exhaustion on a steep uphill treadmill test.
From the other direction, Guillaume Millet blocked off blood flow to an arm with a blood pressure cuff and had subjects perform arm flexes in an altitude chamber. There was no blood getting to the arm, so blood oxygen was constant to the muscles - but at 23k ft simulated altitude, time to exhaustion came 10-15% sooner - a consequence of lower brain oxygenation.
At altitude, in fact, your brain throttles muscle activation pre-emptively - and in trials to exhaustion, your muscles show less fatigue (as measured by electrical stimulation to measure the gap between mental activation and capability) than at a sea-level exhaustion trial.31
When brain oxygen levels drop, so does performance.
What can be done to mitigate this?
Supplemental oxygen
Train at altitude, and if possible, travel back in time so you’re born at altitude.32
Heat
The human body is a machine that takes in food, and burns it in little cellular furnaces along with the oxygen we breathe. All machines have an “efficiency,” ie what percent of the energy taken in goes into productive work.
Modern cars get about 30-35% efficiency, with the rest going out the tailpipe and radiator. Humans are about 20-25% efficient. That is to say, for every 100 calories you eat, about 20-25 of that actually ends up moving you or producing useful work, and 75-80 calories turns into heat.
Although usually we emit a steady 100w, cycling at 250 watts nominal generates as much as 1,000 watts of excess heat. Running at 10 miles per hour produces 1,500 watts.
Picking up a 500lb deadlift over 2 seconds takes an amazing 6,000 watts, 5kw of which is waste heat. Thankfully, nobody is doing this for an hour at a time, because they would literally cook themselves.
There’s a hard temperature your body+brain combo typically won’t allow you to exceed and it’s a core temperature of around 104-104.5 F - when your core approaches that “critical temperature,” you give up or drastically dial back output.
This has some interesting implications for training and performance.
If you look at the top marathoners over time, they’ve been steadily shrinking - the reason is that the heavier and taller you are, the more volume you have generating heat relative to your surface area available for dissipating heat, and that becomes a limiting factor in terms of running at a fast pace for more than 2 hours.
For ultra-endurance endeavors, one of the interesting conclusions to come out of Herman Pontzer’s Burn is that BMR is basically king - there’s a roughly 2.5x BMR energy expenditure limit that applies to any prolonged athletic endeavor, with pregnancy clocking in just shy of 2.5x BMR for 9 months one of the longest examples, but with multiple others such as the Tour de France and Race Across the USA.
But the only independent variable in the BMR equation is your weight! So why aren’t most ultra-endurance events dominated by really big people? There are multiple reasons, but one of the biggest is heat generation vs dissipation being more unfavorable. Another is food and digestive efficiency, which we’ll get to later.
But this DOES argue that if you’re bigger, you have a chance of turning in great ultra-endurance results, as long as you can manage heat well, or choose events in mountains or water, or in colder climates.33
Your body+brain combo knows heat management is important, by the way - studies have shown that athletes setting out to run 10k on a hot summer day have a slower pace right from the start, even before they’ve warmed up.
So if heat is so important to manage, and you can’t necessarily make yourself much smaller or much larger in surface area, what can be done?
Exercise in heat to promote adaptation. 60-90 minutes of moderate exercise in high heat conditions per day produces changes in a day or two, and full adaptation in about 2 weeks.
Drink “crushed ice slurries,” more popularly known as slushees or slurpees. Not only does drinking it have psychological cooling effects, the ice→water phase transition can lower core temps by as much as 1 degree F, and there may be additional benefits from face / sinus cooling.
Cool yourself before a race or performance - soaking in cool or cold water beforehand lowers core temperature and allows greater power output.
Positive self talk specifically around heat management and capabilities allowed an improvement of 8-11 minutes in time to exhaustion and core temps a half a degree higher.
As always, amphetamines, but they are risky in this context. They allow you to push your core temperature higher, without feeling hotter. This can runaway into heat stroke and even death, so be careful.
Perception - cooling vests or outfits, wet towels on the head, and thermometers deliberately jiggered to lie and say it’s a lower temp all improve times, so perception of temperature is at least a noticeable factor (because athletes rarely push so hard they hit the hard “critical temperature”).
Thirst.
People overindex on hydration now, and Hutchinson makes a pretty decent argument you shouldn’t hydrate based on body weight percentage loss thresholds, but on thirst.
Dehydration is rarely a serious problem or risk.34
The important thing is plasma osmolality - the level of minerals in the bloodstream, and this basically goes by thirst rather than bodyweight lost.
Most of the studies on dehydration are absolute dogshit anyways.35
In fact, he points out an interesting fact I didn’t know - doubly labeled water experiments show that for every pound of weight loss, circulating water in the body drops only 0.2 pounds.
This is because the rest of the weight loss is from fat and carb burning to fuel your efforts, the metabolic processes of which release phosphates with the waste products being CO2 that you breathe out, and water which stays in your cells, available to your body.36
So basically, drink when you’re thirsty, and don’t worry about it that much.
“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 to hold you back from a top performance.”
Stephen Cheung - Environmental Physiologist and avid cyclocross racer
Fuel.
Going til exhaustion means going til there’s actually zero glycogen in the depleted muscles.37 Muscles that get those glycogen reserves depleted which then have ample blood sugar super compensate and pack as much as twice as much glycogen in during recovery. Hence carb loading.
Another fun fact - your liver packs about 400-500 calories worth of glycogen reserves, while an athlete’s legs have about 1k calories each. This is why it’s useful to eat the morning before a marathon - your muscles might be fully stocked, but your liver is depleted because those reserves fuel your brain while you’re sleeping.
Eating carbs is a way of life for serious endurance athletes,38 so I’m going straight to the more interesting question Hutchinson tackles:
Do low carb diets have a place for serious endurance athletes?
This was particularly interesting for me - I’m a “power” athlete by inclination. I also eat low carb most of the time I’m not training for a triathlon, and do a lot of HIIT. I knew to carb load while training and before running a triathlon, but I didn’t actually know that my HIIT peaks are likely noticeably limited by eating low carb outside of those windows.
So why eat high fat, low carb? On the one hand, if you burn primarily fat, you come with a much bigger tank, because fat reserves are abundant, and each gram of fat has 2x+ the energy as a gram of carbs. And athletes who eat high fat and do carb-depleted training have very high fat metabolism, getting 85-90% of energy in exertion from fat rather than carbohydrates.39
It’s also been shown that athletes put on a low carb, high fat diet have unchanged VO2max and multi-hour time to exhaustion.40
But the metabolic processes that turn fat into ATP require more oxygen, which reduces your capacity at the limits (above 70% VO2max, generally). Worse, sprinting requires carbohydrates, and a recurring effect seen when testing low carb, high fat athletes is that their sprint performance suffers.41
So if you’re in a field that doesn’t require sprints and moments of true racing - ultramarathons, grueling endurance trials like Mountain to the Sea or Race Across America or the TransEurope Footrace and similar, you might consider it. Otherwise, carb load at least the week before races.
There’s some signs you should train fasted occasionally to upregulate fat metabolism capabilities anyways42 - Hutchinson points to the Australian “Supernova” study43 that tested LCHF diets in Olympic hopefuls. Although they did poorly while on the diets themselves, after being restored to a high carb diet, multiple study participants set national records, and several others notched personal bests.44
Other “fuel” thoughts?
There’s some signs you can circumvent the “60g of carbs per hour” limit by combining two different types of sugar, like fructose and glucose, and get up to 90g an hour.
If you’re mountaineering or going on arctic treks, being fat adapted seems like it has some real benefits.45
Swishing carb-containing drinks and spitting it out works as a transient boost.
Other Stuff
tDCS - transcranial direct current stimulation. As Hutchinson puts it, it is “a sea of bullshit and bad science” with thousands of papers of dubious veracity.
But there might be enough “there” there to give it a try and see if it works for you.46
Perception once again - multiple times in the book, he relates stories of athletes turning in personal best performances when due to miscommunication, they think their splits are faster than they are. This is the “you gauge how well you’re doing by how you feel vs how you predicted you’d feel at this point,” and harnessing it deliberately may be a key to a one-off peak performance.
Perception hacks are almost certainly not something you can use regularly though - you’d just mess up your split timing and prediction engine, and probably perform worse overall.
What will you get from reading the book that you didn’t get from this review?
A lot more fun stories, anecdotes, and flavor, including some guy deadlifting a Camaro to free somebody trapped underneath, somebody becoming so dehydrated they resemble a living corpse, and much else.
If you love stories about arctic expeditions and explorers, MAN is this the book for you - 10% of the book must be about various arctic expeditions!
Insight into his own mental processes and a better picture of the areas there’s ongoing debate and contention in the sport science world (spoiler, everything is contentious).
At least if you’re me,47 more respect and admiration for Nike and Red Bull, given the significant amounts they spend and how serious they take testing and pushing the limits of human performance.
More comes through regarding the personalities of the various athletes and scientists Hutchinson talks to, as well as Hutchinson’s own personality and personal experiences re athletic performance.
A bunch of fun factoids and ideas and depth I didn’t have the space or context to include.
Hutchinson cites an N=20 “random adult” study that sees 41% improvement in pain tolerance and 148% improvement in race day performance (vs 38% improvement in moderate exercise controls).
But umbrella analyses and single studies see good effects from HIIT in trained athletes as well (DOI: 10.1111/sms.14652 , doi:10.1016/j.heliyon.2023.e16663).
There are studies, but more important and meaningful than the studies (to me) is that this is also advice that several high-level coaches live by, too, so it has more chances of working in the trenches.
Morree, Morcora, The Face of Effort: Frowning Muscle Activity Reflects Effort During a Physical Task (2010) and Frowning muscle activity (2012)
For smiling faces, think family / friends at key points of your course, Hutchinson relates doing this and having friends hold up poster boards that make him laugh. For actual studies, there was one looking at subliminal sad / happy faces, and the delta was 22m / 24m to exhaustion.
(A. Blanchfield et al Non Conscious Visual Cues (2014))
For positive self talk, this keeps coming up often enough in multiple studies, and also seems to be used a lot by militaries, so it’s probably worth a try.
Here’s one study Hutchinson cites: A. Blanchfield et al Talking Yourself Out of Exhaustion (2014)
In book Hutchinson cites Samuele Marcora taking a 9 hrs-per-day multiple day motorcycle trip, and measuring days-end having 350ms reaction times (or 450 at altitude) vs 300ms in mornings. But caffeine gum after lunch entirely mitigated the reaction time slowdown.
F.C. Wardenaar et al. Nutritional Supplement Use by Dutch Elite… (2017)
I’m of two minds on this one - obviously, whatever study they ran to show that “sticking to a budget” can improve times is ridiculous p-hacked garbage. But at the same time, although “conscientiousness” is largely innate, “discipline” is to a significant extent amenable to training, as any military can tell you. And re militaries, there are certainly interventions that can help you increase your own personal discipline, and done right, maybe using your non-dominant hand or sticking to a budget could be one of those things.
Shut up, legs! Also being the title of his autobiography, endearingly.
“While great riders are often distinguished by the extremes of their physiology or their grace in the saddle, Voigt’s singular characteristic during an eighteen-year professional career was his appetite for suffering. His ‘open acknowledgment of pain as a state of mind to be ‘combated, repressed and ultimately overcome,’ Cycling Weekly opined, ‘is perhaps part of the reason he is revered by cycling fans as the hardman of the peloton.’”
In a marathon, more like 10-20%, for 100 miles, up to 45%, in Tour des Geantes, a 200 mile ultra-endurance, back to 30%ish, so there’s definitely noise. But even at the maximum 45%, that’s still more than 50% muscular capacity - and you’re going slow enough you’re well below that threshold.
One of the more interesting factoids in the book that I didn’t know was that muscles actually reduce output as glycogen is depleted, aka full glycogen helps muscles activate at maximum strength - it’s like tying the speedometer to the level of gas in the tank.
In a “flexing arm test at 100% effort” - injecting adrenaline increases strength 6.5%, shooting a gun unexpectedly 7.4%, amphetamines 13.5%
Michio Ikai, Arthur Steinhaus, Some Factors Modifying the…, Journal of Applied Physiology (1961) https://doi.org/10.1152/jappl.1961.16.1.157
“They piloted Pervitin: Fabienne Hurst, “The German Granddaddy of Crystal Meth,” Der Spiegel, May 30, 2013; Andreas Ulrich, “Hitler’s Drugged Soldiers,” Der Spiegel, May 6, 2005.”
The most notable failure mode was Roger Riviere’s - he was taking Palfium “an opiate three times more potent than morphine” during the Tour de France, got so numb he couldn’t pull the brake levers, then flipped over a low wall and fell 60 feet, breaking two vertebrae and living the rest of his life paralyzed.
Probably yes - Riviere was riding for Jacques Anquetil’s team, and Anquetil won the entire TdF five times, (57, 61, 62, 63, 64), and even in 58,59,60 placed 3rd overall.
Interestingly, there’s a sharper “altitude effect” at relatively lower altitudes (say 2-3k ft) for trained athletes that doesn’t effect untrained people. This is because in trained athletes, the heart is so powerful that it pumps blood throughout the body so fast, it barely has time to load up on oxygen in the lungs. So in trained cyclists, VO2max dropped by ~6% in trained cyclists at 1900 ft, but there was zero drop in untrained cyclists.
“Even at sea level, about 70 percent of male endurance athletes start to see measurable drops in arterial oxygen levels during all-out exercise, when the heart is pumping most powerfully. (The pattern is even more pronounced in women and older athletes.)”
K. Constantini et al, Prevalence of Exercise-induced Arterial Hypoxemia in Distance Runners at Sea Level, (2017)
Like most of the best Kenyan runners. All the elite Kenyan, Eritrrean, and Ethiopian distance runners like Eliud Kipchoge were born, grew up, and train in the Great Rift Valley at 6k ft above sea level. Shalane Flanagan, the second fastest marathoner in US history, was born in Boulder (5,430 ft). Ryan Hall, the fastest American born male marathoner grew up in Big Bear Lake (6,752).
When you start exercising, brain oxygen initially rises, but then declines over time. Studies looking at brain oxygen in college-level 5k runners showed that blood oxygen was lower at the end of the trial - but studies on elite Kenyan marathoners show no such drop. This is likely a result in the Kenyans of being born in and training at altitude.
Rodney Siegel et al., “Ice Slurry Ingestion Increases Core Temperature Capacity and Running Time in the Heat,” Medicine & Science in Sports & Exercise 42, no. 4 (2010)
On face / sinus cooling, there are some signs that it’s brain temp that dictates the limit, and if your brain is cooler you can push a little bit further on core temp.
P.J. Wallace et al, Effects of Motivational Self Talk… (2017)
With the famous example being Tom Simpson in the 1967 Tour de France.
Especially if you’re bigger, this is more of a risk due to the higher heat you produce and the lesser surface volume you have to dissipate it with - 50/58 NFL deaths between 1980 and 2009 were linebackers.
“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.”
E.S. Chambers et al, Carbohydrate Sensing in the Human Mouth, (2009)
Repeating a “sleep low carb and train empty” cycle three times over 6 days produced a 3% improvement in 20km cycling times.
L.A. Marquet et al, Enhanced Endurance … and Periodization of Carbohydrate Intake… (2016)
Hutchinson points to the Australian “Supernova” study by Louise Burke that tested LCHF diets in Olympic hopefuls. Although they did poorly while on the diets themselves, after being restored to a high carb diet, multiple study participants set national records, and several others notched personal bests, but this was specifically in racewalkers who don’t usually exceed 70% VO2max.
Increased simple muscle flex endurance 10% when stimulating motor cortex, increased peak power 4% on ride to exhaustion for national level cyclists.
Samuele Marcora again - Hutchinson actually tries this in the book, spending hours a day before his marathon doing grindingly boring attention tasks to try to acclimate him to higher levels of mental fatigue. He bonks in the race due to muscle failure and turns in a bad time, though, so hard to say whether it helped. Marcore claims the UK army is seeing big results through a combined physical + brain endurance regime.
Hutchinson’s verdict was that it takes an astonishing amount of time, and he didn’t notice any improvement in splits. He didn’t test himself with Stroop or anything else, either.
The “reverse VO2max protocol” involves starting quickly on the treadmill, then gradually reducing the pace during each 2-minute stage to *just* the point your legs can still handle. Hutchinson describes it as “literally gut-churningly hard” and vomits afterwards.
Subjects doing this attain a ~4% higher VO2max than measured the standard way, and when retested the standard way, retain the higher VO2max.
Tragically for the 2 hour barrier, Kiptum just died in a car crash and Kipchoge is either suffering health problems or has peaked as an athlete, given the sharp decline in his times.
John Landy, Lazlo Tabori, Brian Hewson, Derek Ibbotson
Halperin et al. Pacing Strategies During Repeated Maximal Voluntary Contractions (2014).
Look at the big jumps at 3, 3:30, and 4 - https://imgur.com/a/6X7wBZK
A grueling pain-fest where athletes cover 2,789 miles over 64 days with no rest days
Martyn Morris and Thomas O’Leary, Learning to Suffer… (2017).
But HIIT has benefits for trained and elite athletes too (DOI: 10.1111/sms.14652 , doi:10.1016/j.heliyon.2023.e16663) - everyone should be doing HIIT. It also shows up as one of the practical “mitigating interventions” for 3/5 of these categories.
Some experiments involving elite powerlifters, some combination of electricity and amphetamines, and secret Soviet labs? There are still limits to the human body only known because of unethical Nazi experiments, after all.
"Evidence that Reduced Skeletal Muscle Recruitment Explains the Lactate Paradox… Journal of Applied Physiology (2009)
When you start exercising, brain oxygen initially rises, but then declines over time. Studies looking at brain oxygen in college-level 5k runners showed that blood oxygen was lower at the end of the trial - but studies on elite Kenyan marathoners show no such drop. This is likely a result in the Kenyans of being born in and training at altitude.
Look at Atlantic Dash competitors and winners, for example
“At marathons, triathlons, and cycling races around the world, researchers have tried a simple test: weigh athletes before and after the race, and look for a relationship between race finish and degree of dehydration.
The results are consistently the opposite of what you would expect: the fastest finishers tend to be the most dehydrated.”
“As for the relatively common sight of athletes needing assistance or even collapsing after the finish of a long race, there are several reasons to be suspicious of the idea that these athletes are paying the price for insufficient hydration. One is that studies have found no difference between the typical dehydration levels of collapsed athletes and those who walk away from the finish line untroubled.”
“The 1966 U.S. Army study described earlier in this chapter, which found that being dehydrated by 2 percent caused a 22 percent decrease in time to exhaustion. To achieve this level of dehydration, the subjects had first walked to exhaustion on a treadmill, then spend six hours confined to a room at 115 degrees to promote sweating—all before even beginning their exercise test. Other studies have used diuretics to promote dehydration, and most forbid the subjects from drinking during the bout of exercise. It’s not remotely surprising that endurance is reduced under these conditions: in addition to being dehydrated, the subjects are tired, thirsty, and probably pretty annoyed by the whole process.”
“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. The study with South African soldiers seemed to confirm these estimates, as did a 2011 study by Tam that found no change in total body water content in runners at a half-marathon despite an average weight loss of more than three pounds.”
As verified by a couple of heroic Swedish scientists - Jonas Bergstrom and Eric Hultman in the 60’s, who each pedaled with one leg to exhaustion on opposite sides of an exercise bike, then biopsied both their exhausted and rested legs to look at the glycogen differential between them.
Elite Kenyan runners get 76.5% of calories from carbs, Ethiopians 64.3%
Broadly, they get fat metabolism from mid 50’s percents to high 80’s percents as a percent of their energy
S.D. Phinney et al, The Human Metabolic Response to Chronic Ketosis…(1983)
Sprint performance suffers by ~12% - average 420w for 1km on high carb, vs 370w on high fat low carb (with carb loading the day before the race!). See here: https://imgur.com/a/uOZaBlN
L. Havemann et al, Fat Adaptation Followed by Carbohydrate Loading Compromises High Intensity Sprint Performance, (2006)
L.M. Burke and B. Kiens, Fat Adaptation for Athletic Performance: The Nail in the Coffin?, (2006)
You can certainly improve your fat metabolization from mid 50’s percents to high 80’s percents. Also, repeating a “sleep low carb and train empty” cycle three times over 6 days produced a 3% improvemenet in 20km cycling times.
L.A. Marquet et al, Enhanced Endurance … and Periodization of Carbohydrate Intake… (2016)
Louise Burke et al. Low Carbohydrate, High Fat Diet Impairs…(2017)
Note that this was specifically in racewalkers who don’t usually exceed 70% VO2max, however. But there are likely generalizable benefits from being more efficient at metabolizing fat, because at all speeds, you metabolize some portion of fat vs carbs, regardless of how carb loaded you are.
Hutchinson is just obsessed with Polar treks - He talks about Shackleton often, he goes over Worseley’s three expeditions, Stefansson and Schwatka’s expeditions, etc. But obviously, eating a high fat diet is more necessary in those conditions, and following Inuit practices and diet is how many of them survived.
He does at least work in my favorite quote - Shackleton to his wife when he returned to England: “A live donkey is better than a dead lion, isn’t it?”
Some of the papers Hutchinson points at: Increased simple muscle flex endurance 10% when stimulating motor cortex, increased peak power 4% on ride to exhaustion for national level cyclists.
I’m a barefoot runner and swimmer primarily, who either doesn’t wear shoes or wears zero drops and never drinks energy drinks, so pretty far outside the Nike or Red Bull respective marketing spheres.