What Doesn't Kill Us

by Scott Carney

The Western-lifestyle makes it all-too-easy to take nature for granted. All mammals share the same underlying physiology, but somehow humans are so caught up thinking big thoughts with their big minds that they’ve come to believe that they’re different from everything else around them. Sure we can build skyscrapers, fly airplanes and simply turn up the thermostat to combat the cold, but it turns out that the technologies that we believe are our greatest strengths are also our most tenacious crutches. The things we have made to keep us comfortable are making us weak.

What is hard to communicate to the rest of the world is that what we are doing on the mountain is not a stunt or a suicide mission. The lack of clothing, the altitude, and the pace are actually part of an experiment to understand one of the most pressing questions in the modern world today: Has dependence on technology made us weak? Just about every person I know, from the skeptical journalist in Colorado to the US Army scientist to the guide by my side, envelops themselves in a cocoon of technology that keeps them safe, warm, and helps them endure the natural variations of our planet. In the past six million years of human evolution our ancestors mounted expeditions across frozen mountains and parched deserts with only a whisper of technology to aid them. While they might not have aimed to get up this particular mountain, they surely crossed the Alps and the Himalayas, navigated oceans, and populated the New World. What power did they have that we have lost? More important, is it possible to get it back? The underlying hypothesis of this expedition is that when humans outsource comfort and endurance they inadvertently make their bodies weaker, and that simply reintroducing some common environmental stresses to their daily routines can bring back some of that evolutionary vigor. Every person in this line of wobbling headlamps is potentially putting their life on the line to test the theory. We also know that along with the act of conditioning ourselves over time, there’s a...

Until very recently there was never a time when comfort could be taken for granted—there was always a balance between the effort we expended and the downtime we earned.

Each age let us depend more on our ingenuity and less on our basic biology until technological progress was poised to outpace evolution itself. And then, sometime in the early 1900s, our technological prowess became so powerful that it broke our fundamental biological links to the world around us. Indoor plumbing, heating systems, grocery stores, cars, and electric lighting now let us control and fine-tune our environment so thoroughly that many of us can live in what amounts to a perpetual state of homeostasis.

With no challenge to overcome, frontier to press, or threat to flee from, the humans of this millennium are overstuffed, overheated, and understimulated. The struggles of us privileged denizens of the developed world—getting a job, funding a retirement, getting kids into a good school, posting the exactly right social media update—pale in comparison to the daily threats of death or deprivation that our ancestors faced. Despite this apparent victory, success over the natural world hasn’t made our bodies stronger. Quite the opposite, in fact: Effortless comfort has made us fat, lazy, and increasingly in ill health.

There is a growing consensus among many scientists and athletes that humans were not built for eternal and effortless homeostasis. Evolution made us seek comfort because comfort was never the norm. Human biology needs stress—not the sort of stress that damages muscle, gets us eaten by a bear, or degrades our physiques—but the sort of environmental and physical oscillations that invigorates our nervous systems. We’ve been honed over millennia to adapt to an ever-changing environment. Those fluctuations are ingrained in our physiology in countless ways that are, for the most part, unconnected to our conscious minds.

Today tens of thousands of people are discovering that the environment contains hidden tools for hacking the nervous system. But no matter what they might be able to accomplish, they’re not superhuman. The fortitude they find comes from within the body itself. When they forego a few creature comforts and delve more deeply into their own biology they’re becoming more human. For at least half a century the conventional wisdom about maintaining good physical health has rested on the twin pillars of diet and exercise. While those are no doubt vital, there’s an equally important, but completely ignored, third pillar. And what’s more? By incorporating environmental training into your daily routine, you will achieve big results in very little time.

To stave off hypothermia, the body conserves heat by shutting off blood supply to the extremities. When this happens, miles of vestibular roadways squinch closed, keeping most of the blood in the body’s core and letting the vital organs relax in a warm blood cocoon while temperatures in the hands, feet, ears, and nose plummet. The colder it is outside, the stronger the response. For a person not regularly conditioned to temperature shifts, vasoconstriction is painful. The only way that most of us can trigger the muscle response is to actually go outside and feel the cold. And those of us who live in perpetually climate-controlled environments never exercise this part of our circulatory system. Weak circulatory muscles are a side effect of living in a very narrow band of temperature variation. The vast majority of humanity today—the entire population that spends the bulk of its time indoors and/or whose only experience when it gets too cold or too hot is wearing state-of-the-art outdoor gear—never exercises this critical system of their body. Even people who appear physically fit, with lean muscles and chiseled abs, might be secretly hiding weak circulatory muscles. And the stakes are huge: In the long run, circulatory diseases contribute to almost 30 percent of the world’s mortality.

But what happened when humans gained so much technological skill that they effectively dominated their environment? All human technology originates out of the activity of our higher brain functions. In a way, our conscious minds are now so in control of the world we live in that they’ve left our lizard brains out of the loop. Without external signals and inputs that were designed by evolution over millennia, our bodies are simply not being called upon to perform what have always been critical functions. That internal programming lies dormant and unproductive.

For most of our evolutionary past, comfort was a rare treat and stress was a constant. The lower parts of our brain formed in environments where there were always physical challenges to overcome, and those challenges were part of what made us human in the first place. Despite all of our technology, our bodies are just not ready for a world so completely tamed by our desire for comfort. Without stimulation, the responses that were designed to fight environmental challenges don’t always lie dormant. Sometimes they turn inward and wreak havoc on our insides. An entire field of medical research on autoimmune diseases suggests they originate from fundamental disconnect between the outside world and an understimulated biology. This book is largely about what happens when we reexamine our relationship with the environment and see ourselves as a part of something bigger than the comfortable spaces we mostly choose to live in. It explores how changing the environment around the body also fundamentally changes the body itself. More importantly, it shows how it is possible to manipulate our external environment to trigger autonomic responses in predictable ways. Once you realize that you can manipulate deep parts of your physiology by intentionally tweaking identifiable preprogrammed responses, you can begin to cede aspects of that automation to your consciousness.

This is the moment that I decide that I will have to reevaluate everything that I thought I knew about gurus. Still, Hof is a difficult figure to dissect. On one level he speaks in a familiar creole of New Age mumbo jumbo. There’s a spiel about universal compassion and connection to divine energies. And he has a way of descending into long monologues about how a few simple exercises might foster world peace and, as he says, “win the war on bacteria.” After an hour or two of listening to grandiose and even self-congratulatory claims, it is easy enough for me to let my eyes glaze over and ponder the charlatan idea a little more seriously. Then, of course, there are the results. The relatively simple exercises make undeniable changes in my body seemingly overnight. Following his prescriptions for a week straight, I will cajole my muscles into performing feats of endurance that I didn’t think were possible, and earn a confidence I didn’t know I had. As a bonus, I will lose 7 pounds of fat—which mostly come out in oily clumps during my morning eliminations.

Then, in the winter of 1979, when he was 20 years old, he found it. While walking alone on a frosty morning in Amsterdam’s picturesque Beatrixpark, he noticed a thin skin of ice on one of the canals. He wondered what it would feel like if he jumped in. With a juvenile impulsiveness he has never quite shed, he took off his clothes and plunged in naked. The shock was immediate, he says, but “the feeling wasn’t of cold; it was something like tremendous good. I was in the water only a minute, but time just slowed down. It felt like ages.” A wash of endorphins cruised through his system, and the high lasted through the afternoon. He has gone on to repeat the exercise just about every day since. “The cold is my teacher,” he says. The breathing technique emerged naturally. He started by mimicking the rapid breaths people take instinctively when they plunge into icy water, which he says are similar to the breaths a woman takes during childbirth. In both cases the body switches to an instinctual program. When Hof dunked under the ice, his body went naturally from rapid breathing to a breath hold. That’s when he began to feel changes in his body. The way Hof explains it, humans must have evolved with an innate ability to resist the elements. Our remote ancestors marched across endless expanses of frosty mountains and navigated parched deserts long before they invented the most basic footwear or animal-skin coats. While technology has made us more comfortable, the underlying biology ...

In that now-famous segment, Hof cut holes in the ice and jumped in while the news crew filmed. He was drying himself off when, a few meters away, a man stepped on a thin patch and fell through. Hof charged out onto the lake, jumped in a second time, and dragged the man to safety. The news crew caught the exchange, and soon Hof wasn’t just a local oddity, he was a local hero. Someone dubbed him the Iceman, and the name stuck.

Although the first day of exercises is painful and exhausting, true to Hof’s word our progress is rapid. The next day we stand in the snow for 15 minutes before the same feeling of panic sets in. In the afternoon we take a brief dip in the basin of an ice-cold waterfall that is a 5-minute walk from Hof’s back door. With every attempt, the barriers that we’ve built in our minds about the cold recede a little further.

In 2007, at the Feinstein Institute for Medical Research on Long Island, Kenneth Kamler, a world-renowned expedition doctor who has worked on Everest, observed an experiment in which Hof was connected to heart and blood monitors and immersed in ice. At first the experiment hit a major snag. The standard hospital devices that track respiration declared him dead after he’d been in the ice only 2 minutes. The machine got confused because he hadn’t taken a breath and his resting heart rate was a mere 35 beats per minute. He wasn’t dead, though, and Kamler had to disconnect the device to continue. Hof stayed in the ice for 72 minutes. The results were astounding. Hof’s core temperature initially declined a few degrees but then rose again. It was the first scientific validation of Hof’s method. “Exactly how you explain it depends on the kind of philosophy you want to believe in,” says Kamler when I later track him down on the telephone. He references similar feats called tummo performed by Tibetan monks where they modulate their body temperature with breathing and intense visualizations of tantric deities. Ultimately, he says, it boils down to how Hof uses his brain. “The brain uses a lot of energy on higher functions that are not essential to survival. By focusing his mind, he can channel that energy to generate body heat,” he speculates.

Brown fat is different. Most people create it automatically when they’re in cold environments by way of a process called beiging. Essentially, the body detects physical extremes and starts to store mitochondria. When brown fat starts to work, the mitochondria suck white fat through the bloodstream and metabolize it directly to generate heat. Because most people do everything they can to avoid environmental extremes, they never build up brown fat at all. If we lived without clothing the way our distant ancestors must have, then we would have to rely on the internal properties of brown fat to keep us alive during the winter months and cold nights. As we sit in the sauna, I ask Hof how someone activates brown fat consciously. Instead of explaining, he launches into a demonstration. He clenches the muscles in his body in sequence, from his toes to his rectum then from there up to his shoulders, as if pushing something up from below. Then he furrows his brow and squinches down his neck as though he is trapping that energy in a point right behind his ear. The process turns his skin bright red, as if he is catching fire. Suddenly he kicks out his leg and falls against the wall gasping. “Oh my God,” he says, dazed. In his eagerness to teach, he didn’t factor in the heat of the sauna and almost blew a fuse. He lurches out of the sauna and rolls in the snow outside. The few of us pupils exchange concerned glances, but in about 15 minutes he returns with an embarrassed smirk. “That’s...

While Hof meditated, Pickkers and Kox injected him with the endotoxin. The results were unheard of. “Wim had done things that, if you had asked me prior to the experiment, I would not have thought possible,” Pickkers tells me. Whereas almost every other person dosed with endotoxin experienced severe side effects, Hof had nothing more than a minor headache. Blood tests showed he had much higher levels of cortisol—a hormone usually released only during times of extreme stress, sort of like adrenaline—than Pickkers had recorded in any previous study. Also, blood drawn while he was meditating remained resistant to endotoxin for 6 days after it had left his body.

The moment I take off my shirt I start to get a sense of how our primordial ancestors would have handled the same march. Trudging forward I don’t feel the bite of the cold the way I did before undergoing the regime at camp. Whatever heat I build up through exertion seems to stay in my skin as if I am wearing a wetsuit. I can feel the cold, but it never penetrates. I never shiver. Instead, I focus on the point behind my ears that Hof says will help activate my brown fat and send waves of heat through my body.

The strangest thing is that we aren’t suffering at all; we are elated. Cold and exercise trigger an enormous endorphin release that pastes a maniacal grin across my face. It is as if the temperature is subservient to the task ahead. Six hours later I near the summit, bare-chested and with my legs caked in snow. In just a week I’ve gone from California palm trees to Poland’s snowy peaks and I feel perfectly warm—hot, even.

Just like when I walked into the sauna after standing in the snowy field that first day of camp, the warm air of central heating sends a shock through my system. A minute earlier I felt immune to the elements and happily cavorted in the snow, but now that I am out of harm’s way and have begun to relax I feel a new creeping, cold sensation. My mental armor is gone and the ice in my extremities leaks into my bloodstream. Warm environments are supposed to make me feel warm, but that’s not what is happening. Things are backward. At first a small shiver escapes up my spine. A minute or two later it is a full blown shake. My teeth clatter audibly and soon I can’t remember ever being this cold before in my entire life. This, I will learn later, is what paramedics who rescue hypothermic patients call “afterdrop.” During vasoconstriction the limbs get much colder than the core. When the body starts to warm up, it lets blood through the vascular system again. Blood chills as it passes through the cold arms, hands, and feet, and when it eventually circulates back to the heart it lowers the body’s overall core temperature. In extreme cases, afterdrop can be fatal. An hour elapses before I feel ready to get back on my feet for the climb down the mountain.

While supertasting does not have much of a profound effect on most people’s daily lives, the existence of supertasters offers a peek into to the strange world of sensory perception. Indeed, PTC sensitivity is far from the only recently discovered sense. There are people who can see more than 100 million colors (the normal human can distinguish about 2.4 million), an ability called tetrachromacy. There are people who have the ability of absolute pitch and are able to listen to a note on a piano and instantly recognize its frequency without needing another tone for reference. There are blind people who can navigate through the world by clicking their tongues and listening to the echoes—an ability that they share with bats and dolphins. Some people’s sensory hardware scrambles the inputs between senses so that they can taste colors and hear smells, a condition called synesthesia. The neurological jumble usually doesn’t interfere with synesthetes’ daily lives, and indeed many go on to be extraordinarily successful and creative—from the author Vladimir Nabokov to the scientist Richard Feynman.

However, after many contentious debates carried out over the course of a decade, researchers reached a consensus that whether the cause was magnetism or some other aspect of underlying biology, humans do indeed have an innate directional sense. It’s just that we don’t use it very much anymore.

A recent study of cab drivers in London offers a glimpse into how wayfaring corresponds to specific brain structures. In order to get their taxi permit London cab drivers have to memorize the convoluted rat’s nest of English streets and be able to navigate the entire metropolis without maps. Researchers hooked up cabbies to MRI machines and discovered that the longer they drove cabs, the larger the volume of their hippocampi increased. The finding proved that thinking spatially can drastically change the brain. However, and perhaps more interesting, is that once the drivers retired, their brain structures returned to ordinary sizes. It’s strange to think about how quickly a human sense can disappear when it falls into disuse. Even when it is the most defining characteristic of a person, simply not exercising the neural muscle over a short time can make someone entirely dependent on external resources. While digital maps are a fairly recent phenomenon, there are other much more fundamental biological abilities that have simply vanished from our everyday use altogether. They lie there dormant and unused until the right stimulus wakes them up.

Luckily for the human subjects of Swedish-born physiologist Per Scholander, testing methods had gotten more sophisticated over the intervening century. Instead of binding his volunteers to death, he used lab equipment to measure the heart rates and oxygen levels of volunteers while they dove to the bottom of a pool. The second that the cool water covered their faces, Scholander noticed an immediate and corresponding decrease in their heart rates. It was the same phenomenon that Richet has seen with his ducks. In the second phase of the experiment Scholander installed a few pieces of fitness gear at the bottom of the pool and told his subjects to work out while underwater. While the toil of lifting weights underwater must have been awkward, the heart monitors showed that no matter how vigorous their activity was, their heart rates remained suppressed. Not only that, the volunteers also experienced vasoconstriction while beneath the surface of the water as the blood from their extremities shunted toward their core. The water, it turned out, triggered a series of physical changes in his subjects that advantageously prepared them to survive in a hostile underwater environment where breathing would mean death. It’s a reflex that Scholander named “the master switch of life,” a term that has since been taken up by a burgeoning free-diving community that depends on these built-in changes in the body to extend the duration of their underwater forays. Freedivers, described masterful...

It’s not easy to know how many vestigial responses like these lay dormant deep within our human physiology. They are the sorts of abilities that only manifest themselves when the right conditions arise. They are the gift of millions of generations of incremental biological changes from ancestors whose daily challenges we only have a dim understanding of. Because most humans nowadays live within a narrow band of homeostasis, unlocking new responses occurs mostly by chance. And yet, when they do trigger, we are not always conscious enough to notice how they kicked in. In the modern world there are almost no people who are truly “untouched” by civilization. There is no control group that scientists can reference for what a wild human might actually be like. Instead the best we can do is rely on early anthropological literature, first-contact reports, and the mythologies and oral histories of native people around the world.

Brown fat is a fundamental tissue in mammals that, at the time, was mostly understood as something that rodents used to help heat themselves during hibernation. The spongy, fatty tissue looks a lot like ordinary white fat that most mammals use to store excess caloric energy. But where white fat can serve as an insulator, brown fat has an active role to burn white fat to generate body heat. It’s the only mammalian tissue whose sole purpose is to make heat, or, in scientific terms, thermogenesis. In humans, however, BAT was only considered important in newborns. The very first challenge that a human faces once it is born is the constant fight to keep a stable body temperature. With a relatively high ratio of surface area to body mass, babies lose heat much faster than adults. This is why many premature babies spend their first weeks in incubators. The easiest way for an adult to rapidly increase their core temperature is through shivering. The activity of muscles generates a moderate amount of heat as a byproduct of movement. Fresh from the womb, infants lack significant musculature and can’t shiver themselves warm. Instead they are usually born with a layer of chubby rolls of insulating white fat. When their core temperature begins to drop, BAT turns on, sucks white fat from their system, and releases a cascade of heat energy.

Above the Arctic Circle in the Norwegian territory of Lapland, one scientist found that the local reindeer herders had an incredibly strong vasoconstriction response to the cold while at the same time exhibited a pronounced drop in their core temperatures when they slept out in the snow at night. The Lapps, it seems, had discovered a way to simply not be bothered too much by getting cold, and had a much higher threshold before succumbing to hypothermia. But the strategy for surviving the Arctic climate was found not to be the same across all polar-dwelling populations. Inuit subjects who lived in northern Canada showed significant heat loss when given the same test, leading researchers to suspect that they were instead able to passively increase their metabolism. Inuit were also able to keep their hands warm when immersed in cold water, which means they had a blunted vasoconstriction response. This adaptation strategy would have meant that their bodies intentionally sacrificed some of their core temperature in order to have better dexterity with their hands. An anthropologist named H. T. Hammel who studied Aborigines of the central Australian desert in the 1950s observed that even though the tribesmen wore no clothing, they still slept outside throughout the winter when the temperature dropped to just below freezing at night. They slept on bare ground with only a screen of bushes to protect them from the howling winds. While they were asleep, Hammel tested the Aborigines’ ...

The Wampanoag seemed to understand intuitively that resistance to the elements wasn’t an innate power. Instead, they recognized that their bodies already had all the tools necessary to survive in the environment if they made a conscious effort to adapt. It’s the same fundamental biology that probably allowed Neanderthals to survive, and there’s no reason to think that these abilities are not shared by every person alive today.

Every human alive today lives in a cocoon of consistency: an eternal summer. “We’re overlit, overfed, and overstimulated, and in terms of how long we’ve been on Earth, that’s all new,” he says to me while summer is settling in Alabama. We’re missing out on what he calls “metabolic winter,” a time when the body adjusts to discomfort and scarcity between times of plenty. As he writes in his opus article on the subject, “Our 7-million-year evolutionary path was dominated by two seasonal challenges—calorie scarcity and mild cold stress. In the last 0.9 inches of our evolutionary path we solved both.” The inevitable result of losing seasonal variation is obesity and chronic disease. As proof, he doesn’t point only to the population of his home state, which ranks at #5 of the most obese states in the nation, but also to the fact that our pets are fat, too. “The only two animals in the world that suffer chronic obesity are humans and the pets we keep at home,” he says. “There’s a connection.” The key to fixing the problem, according to Cronise, is to artificially reintroduce seasons back into our lives. Drawing on the growing literature on brown fat and metabolic analysis, he prescribed himself daily hour-long walks in sub-60 degree temperatures along with moderate exercise and calorie restriction. In the course of just 6 months, from June to November, he dropped almost 40 pounds.

As Pickels inches up the speed on the treadmill I ask him if maybe I might hide the same sorts of talent as Stevens. He smiles like he gets that question a lot. “No,” he says. “It’s mostly about genetics.” From the moment I walked into the offices in Boulder, he knew that I would never be world class. The dead giveaway, he says, is the one muscle in my body that I always thought I had legitimate reason to be proud of. After a splinter lodged into my heel as a kid I’ve had a tendency to walk on my toes. My loping and oddly bouncing stride caused no shortage of middle and high school teasing, but as a side effect it also gave me abnormally large calf muscles. While they are by far the most toned part of my body, Pickels tells me they’re also a clear predictor that I just don’t have what it takes to be an endurance athlete. “It’s like you’re carrying two pendulums at the bottom of your legs,” he says. “You have to work harder than someone born with long, skinny legs.”

The workout regime itself is relatively simple. Every morning before breakfast I’m going to do breathing exercises, followed by breath-hold pushups and a headstand. It’s a truncated version of the method that Hof recommends for a full hour a day. I choose this abridged routine because it is more manageable and easier to keep track of. When I do work out, it will be outside. For now that means shirtless runs in the sweltering summer heat, but as the seasons gradually progress to fall and winter there will be snow, wind, and hopefully a liberal buffeting of frost. Finally, I’ll take cold showers every morning and, when possible, lie down in the snow like I’d learned to do in Poland. All together, the routine will add between 15 to 20 minutes of exercise to my day and should be easy enough to keep up with throughout the 6 months of the experiment. The key, I think, will be to keep exposing myself to temperature variation and getting comfortable with whatever weather is outside my window. I want to be in touch with the seasons. My goal isn’t to become the next champion ultramarathoner or to build muscle mass or even simply to lose weight. I want to see the effects of introducing variation into my environment and discover what happens when I try to take control of my body’s autonomic processes.

It’s the same wedge that a person uses to calm their nerves when standing in the snow, withstand shivering, hold their breath just a little bit longer, delay an orgasm, stop feeling ticklish, or hold back the flow of urine as they search for a bathroom. It seems like a small thing, but it’s a window into the root of a human power, and a place that, if exercised, can help unlock the body’s hidden biology. Freedivers who descend hundreds of feet below the surface of the ocean on a single breath sometimes call it the “master switch”: It’s the point where the body meets the mind.

So training starts with one of the most fundamental human reflexes: the urge to breathe. When the Buddha first taught meditation to his followers, he recommended that they start by watching their breath move in and out of their body. Breathwork is a staple of every yoga class, as students move their bodies in sync with their lungs. The Wim Hof Method tasks students to hold their breath until they can’t take it anymore. And then hold it just a little longer. This is the quickest and probably safest way to build your own wedge. The urge to gasp for air is not directly linked to the amount of oxygen in the bloodstream. That’s because, for some reason that has been lost in the convoluted process of evolution, the body cannot sense oxygen, only its byproduct. Breathing is a two-part process—inhaling to bring oxygen to the lungs and exhaling to expel carbon dioxide (CO2). When the brain senses too much CO2 in the bloodstream, the chest tightens, vision blurs, and just about every muscle from the abdomen to the forehead clenches down hard. When we talk about this sensation we usually say that we need to take a breath. However, on a physiological level your body wants to expel CO2. It sounds counterintuitive but it’s easy enough to test. Take a deep breath in and hold it until you feel the urge to breathe. Then release a little bit of air. With less CO2 in your lungs you will feel like you can hold your breath a little bit longer. That’s because you’ve removed a potentially poison...

First you will need to establish a baseline. Take a deep breath of air and time yourself with a stopwatch to see how long you can hold it. Most people can hold their breath for between 30 seconds and a minute without any training, but everyone’s underlying physiology is a little different. While you’re at it also figure out how many pushups you can do. When I first started, my arms began to buckle at around 20. Some people can only do one or two. Whatever it is, write down your baseline, perhaps on the inside back cover of this book, so that you can check back on it later. I should note that this is a variation on the Wim Hof Method. It is an even more basic starting point than where he usually begins students with their training, and is not precisely the one that he teaches in his courses. The first goal is to prepare your body by blowing CO2 out of your system. Start by sitting down on a couch or lying on the floor and taking 30 fast breaths. Each inhale should take about a second, but you should not force the exhale. Instead let it flow out naturally. Your breath should sound like you’re at the peak of a sprint just a few seconds shy of having to slow down. Pretty soon you’re going to feel a little dizzy; this is normal. You might also feel tingling in your hands and feet. You might also feel cold. Or experience ringing in your ears. After about 30 breaths you will have radically increased your blood oxygen saturation and cleared out most of the CO2 in your system. Now,...

The autonomic nervous system divides itself into two interrelated components. First is the sympathetic nervous system, which controls the so-called fight-or-flight response. If you were a car, the sympathetic system would be the gas pedal. It gives you short-term boosts in energy, activates the adrenal gland, and triggers dilation and vasoconstriction. The parasympathetic nervous system controls the opposite responses, sometimes called the “feed-and-breed” actions. This is the equivalent of a car’s brake pedal. The parasympathetic nerves act on digestion, salivation, sexual arousal, and tears. Both systems are involved in breathing, and the right techniques can help strengthen both sides of the nervous system. In the same way that someone at a gym can focus on particular muscle groups during exercise, different breathing routines target different aspects of the nervous system. The basic breathing technique of holding your breath after hyperventilating acts mostly on parasympathetic nerves. The sympathetic system only starts to kick in closer to the moment when you are struggling to stop yourself from gasping, and it is often best to train with breath-out holds. Breath-in holds are better for getting to your absolute maximum number of pushups or retention duration, but are less efficient at cracking into your nervous system.

POWER BREATHING In order to prime your body to get to the gasp point earlier (and thus build a stronger wedge and activate the sympathetic nervous system), start with the basic breathing method for approximately 30 quick, deep breaths. Keep your eyes closed and breathe hard enough that you begin to feel light-headed. Now, instead of taking in a deep breath and holding it, let most of the air out of your lungs like you would at the end of a normal breath (by which I mean, don’t force it) and hold your breath with mostly empty lungs. Your body will quickly deplete the oxygen stores available in the lungs and have to rely solely on what is available in the bloodstream. When you get close to needing to gasp, you can extend your limits in two ways. The first is the same as with basic breathing, slowly letting out what is left of the air in your lungs. The second method will become critical later for controlling vasoconstriction. It consists of a rolling set of muscle contractions that you start at your feet and sequentially tighten until you reach up to your head. The process is as follows: Relax your body and clench the muscles in your feet. Then clench your calves, then thighs. Work the contractions up your body until every part of you is tight from the bottom to the top. Clench your stomach, your chest, fingers, biceps, and jaw. Tighten the muscles behind your ears and imagine all of this pressure that you’ve built up going out the top of your head like you were rolling out ...

When you give yourself a way to connect the visual information behind your eyes to the sensations in your extremities you have unlocked a tool for taking control of the process of the immune system itself. The combination of breathing exercises, muscle flexing, and visualization are the basic core exercises of Hof’s training.

The first time that you try to stand in the snow it’s not only going to feel cold, it’s going to hurt. Even though it won’t hurt any more than, say, a 5-mile run, or hitting the gym to lift weights if you’re severely out of shape, the sense of fear that comes from the cold reaches down into some dark primordial core inside every one of us. The mere thought of it makes most people cringe. Your brain is probably screaming, “Hell no!” If you urge your friends to try it, their responses will resemble the various stages of grief: denial that it’s a good idea, anger that you even suggested it, bargaining for some other exercise option, depression (okay, maybe not this one), and, finally, acceptance that it probably won’t kill them. Almost everyone claims that while some people are able to stand in the snow, they themselves are especially vulnerable to the cold. The fact that this is a near-universal response might persuade them, but, perhaps, if you persevere, they might at least try it.

There is nothing special to the technique. You can fill a bucket or bathtub with ice and jump in. You can turn the shower on as cold as it gets and soak for a minute. Or, perhaps the closest to what our ancestors faced, wait for it to snow and then walk outside in nothing but shorts. Whatever the cold source, the goal is to give your system a little shock. Don’t ease yourself into the frigid waters and wait for your body to acclimatize. Jump right in and see how your body responds, like you are doing a polar bear plunge. Start with taking 30-second cold showers and build up from there. The immediate sensations are rarely pleasant. You’ll start breathing fast, your pupils will dilate, and you’ll want to start moving to keep yourself warm. Feet in the snow will often turn red as blood courses through the veins before they turn lighter in color, once vasoconstriction sets in. While you’re in this moment of shock and pain, you have two basic goals. First, you need to control your breathing and keep calm. The sensations that most closely match the feeling of burning will dissipate if you focus your mind on the pain. Try to relax instead of tightly clenching up every muscle. Enduring the snow is the same exact mental trick as trying to delay a sneeze or resist being ticklish. Once you feel reasonably calm, the second thing you need to master is suppressing your impulse to shiver. After the initial shock of the cold recedes, your body will soon click on an instinctual program to ...

This chart will give you some established guidelines for safe cold exposure. Avoid frostbite, but don’t worry too much about just fee...

The first time you experience the cold will be the worst. Every nerve will fire like it is raw and has never been used before. Your heart will race and you’ll want to do anything you can to retreat into warmth. Unless you are in weather where frostbite is likely, you’re not in any serious danger, even though your mind will tell you that you are. The veins in your hands and feet will clench with the force that it reserves for severing a limb. If you are jumping into a cold body of water, go with a friend just in case one of you runs into trouble. Nonetheless, if you last just 5 minutes your entire body will probably be screaming for relief. Go inside and warm up. Most likely, the sensation of vasodilation, when the veins loosen and let warm blood back inside, will hurt even more. For some, the process of rewarming is more painful than the initial exposure. Think of the pain as a sort of baptism. When you try it again the next day, it will be much more manageable. Of course, not everyone has access to cold on demand. If you live in a temperate climate or are in the throes of summer, then you may have difficulty finding a reliable source of icy water. A lot of this is going to be u...

Another very simple technique is what I call active conditioning. This is where you start whatever workout you normally do in one environmental extreme or another. I often will go running in just shorts and sneakers during the middle of winter, when snow has blanketed the Colorado landscape. I do a 3-mile run around a lake near my house without a shirt on while other brave souls are clad head to toe in fleece. Heads turn and most people will think I’m crazy, but anyone who has even a modest running habit knows that once they get moving their core temperature spikes upward. Those fleece-clad joggers are probably boiling up. However, since the nerves in your skin can still detect the weather, outdoor exercise in the cold while shirtless will send the appropriate signals to start generating brown fat. Shirtless runs end up being one of the most comfortable ways to practice the Wim Hof Method. If it’s really cold, it’s not cheating to wear a hat or gloves to ward off frostbite in the extremities.

The same thing goes for hot weather. When the mercury in the thermometer rockets upward, do a run in the middle of the noon-day heat. Don’t push yourself so hard that you pass out from heatstroke, but get used to a slightly uncomfortable temperature. You can do the same thing in any weather, be it rain or shine. Part of the reason humans have gotten weaker as we’ve insulated ourselves with technology is because we don’t experience variety in our daily lives. Make yourself a little uncomfortable, and all of a sudden you might discover that it isn’t nearly as bad as you imagined it might be. One more thing: Remember to wear sunscreen.

BROWN FAT ACTIVATION It seems to take about a week of training before your body recruits enough brown fat (BAT) for it to have a meaningful impact on your metabolism. If you don’t live in a cold climate, it is more than likely that you are going to start out with near-zero BAT. Over time, however, your stores will grow, and that brown fat will passively suck white fat from your bloodstream and burn it for body heat. However, there are moments when you want more than just a little heat over a long period of time. What if you want to get warm right now? After a few weeks of training you can make BAT activate on command. The process for doing it is a familiar one. Once you’re already cold, clench the muscles in your feet and hands and then sequentially tighten every muscle above them. The method is essentially the same as the one you use during power breathing except that now, rather than simply pushing all the blood up to your head in general, you instead focus on a specific point on a small ridge on the backside of your skull where the temporal bone and occipital bone meet just behind your ears. Once you’ve pushed all of your muscles up to that point, you then squinch any muscles...

A 15-MINUTE DAILY WORKOUT My daily routine mixes elements of all these practices, plus a few more I borrowed from a local yoga class. I always start before breakfast, when my circulatory system is the most active and hasn’t yet been weighed down by the process of digestion. I begin with three rounds of power breathing followed by a breath-hold with no air in my lungs. I time myself and try to add a minute to each breath-hold until I hit 3 minutes. Then I do another round of breathing followed by 50 breath-out pushups. I follow this with a headstand for 30 seconds to let blood move to my head. I usually start my shower warm, but finish with at least a minute of cold water. I get out feeling refreshed and pumped full of endorphins. On top of that I do...

In Wim’s terminology, breath-out exercises primarily work on the sympathetic nervous system—the fight-or-flight responses. Breath-in exercises first trigger parasympathetic responses and might make a person more inclined to relax before the sympathetic responses kick in.

In the split second that he realizes that he’s lost control, he thinks about what the crash might be like and then plans to minimize the damage. Whether this means rolling into a ball, diving off the board, or whatever else opportunity puts on his doorstep, he believes that there will always be a moment when he will have a semblance of control again. The trick is waiting for it to happen. The swirling currents and crushing forces are, after all, just forces. They ebb and flow and dispassionately dispense opportunities as they do obstacles. During a crash, the water rushes over his body and asserts its will. In the torrent of water his limbs aren’t his own. He’ll be smashed by water, rocks, the board he was carrying, and whatever else gets in his way. In these moments of utter powerlessness Hamilton submits and relaxes. In the eye of the maelstrom there’s nothing to do but let nature run its course. It will either kill him, maim him, or let him go. The Zen during the tumble is humbling and can tick by for breathless minutes. Hamilton’s lungs might burn and his body might be brutalized by the swirl around him. “But at some point,” he says, “if you make it far enough, the grip will loosen. You have to keep your mind still while you are in the midst of it all, knowing that your chance will come.” And when it does let up, Hamilton taps into all of the stored up energy in his body to make his move. That’s when he lets the fight-or-flight response take over. He uncoils like a jac...

His studies aim to understand the way that the environment alters the body. While pharmaceuticals might be able to target specific bodily processes and tweak them to treat a specific acute ailment, van Marken Licktenbelt sees the twin epidemics of diabetes and obesity through a thermodynamic lens. Both conditions come from there being too much energy available for the body. When there’s too much energy in a system, then that system starts to malfunction. It’s a matter of physics. And there are really only three ways to fix it: You can reduce the amount of energy coming into the body, decrease the body’s efficiency of absorbing energy, or increase the rate that the body makes use of it. Most diets follow the first line of attack. To lose weight, you can simply significantly decrease your food intake. Working on the input side of the equation will result in some short-term success, but more often than not people struggle to restrict their calories and end up regaining their lost pounds over time. Several drugs follow the second line of attack by changing the efficiency with which the body actually processes food. In the 1920s, magazines sold tapeworms for people to ingest and host. With the help of the worm, people could eat whatever they wanted and still lose weight. But parasites are not the most friendly companions, and this treatment often led to severe anemia and malnutrition. A more recent iteration of the same idea is a drug called Xenical. It sets an artificial limit...

The miraculous properties of BAT are just one of many strategies that the body can rely on to accomplish the same tasks. An extremely overweight person with a surplus layer of insulating white fat doesn’t necessarily need to ramp up their metabolism to fight against the cold. The layer of fat alone suffices to protect against moderate exposure.* People who are already in shape, however, might respond much more quickly to cold temperatures, forcing their bodies to generate BAT in order to stay alive. After a series of biopsies to investigate what other possible mechanisms might have helped his patients, van Marken Lichtenbelt discovered that ordinary muscles can also transform under the right conditions and hyperstimulate other cellular mitochondria to accomplish the same results as active BAT. The secrets of the human body are complex and highly dependent on the individual and the method of exposure even if the results are the same. However, more than anything else, this study shows that while a drug might activate one specific pathway to generate heat energy to burn up excess calories, administering that drug might not be the optimal solution. Instead of stimulating the body with a foreign substance, it is probably more efficient to use the environment to trigger the correct and predictable response.

One week after I left Poland after summiting Mount Snezka, three instructors flew to the farmhouse and Hof taught the active group three basic techniques: cold exposure in the snow, focused third-eye meditation, and sequential muscle retention after hyperventilation. They climbed up the same mountain that I did and baked in the same sauna. When they returned from their trip the volunteers continued to practice on their own for 5 days before showing up to Pickkers and Kox’s lab for supervised injections. The results were astonishing. Even after such a short training program the active group showed positive levels of epinephrine as well as an increased amount of anti-inflammatory molecules in their blood. They had fewer fever-like symptoms than the control group experienced, and their cortisol levels returned to normal much quicker. To quote the subsequent journal article from the Proceedings of the National Academy of Sciences: “Hitherto, both the autonomic nervous system and innate immune system were regarded as systems that cannot be voluntarily influenced. The present study demonstrates that, through practicing techniques learned in a short-term training program, the sympathetic nervous systems and immune system can indeed be voluntarily influenced.” This short declarative statement forced the scientific community to completely reevaluate their understanding of the immune system. The article earned a mention on the journal Nature’s website and caught fire across the inte...