As I've written about before, I'm a complete book nerd, and I read a book a day. As an exercise physiologist, I'm especially intrigued with books that delve into the science of suffering (er, exercise) and recently discovered a real gem of title: “Endure: Mind, Body, and the Curiously Elastic Limits of Human Performance“, written by author Alex Hutchinson, who also happens to write some of my favorite exercise science articles on the Runner's World website.
Normally, when I fold over pages and highlight over half of a book, I'd attempt to wrangle an author like Alex onto my podcast, but I'm booked until nearly October of this year, and I desperately wanted to fill you in on his book before then.
So I reached out to Alex and he graciously agreed to give you a customized flavor of what you'll discover within the pages of Endure. In the book, Alex, an award-winning journalist, reveals a wave of paradigm-altering research over the past decade that suggests the seemingly physical barriers you encounter are set as much by your brain as by your body. He explores pain, muscle, oxygen, heat, thirst and fuel and disentangles the delicate interplay of mind and body by telling the riveting stories of men and women who’ve pushed their own limits in extraordinary ways.
Enjoy some of his big takeaways in this article (this article is not in the book!), and let me know in the comments section below the article if you dig it when I get guest authors like Alex to pen an article like this, because I read plenty o' books and can likely do this more in the future.
Take it away, Alex…
My Spring Shock
After 25 years of competitive running, I like to think I know my outer limits pretty well—the tunnel vision, the altered flow of time, the legs full of cement. But I got a shock last spring while reporting on Nike’s Breaking2 marathon project. To give me a flavor of what Eliud Kipchoge and the other top runners in the project we're doing, Nike wired me up with GPS and heart-rate monitors that transmitted all my workout data back to Nike HQ in Beaverton, where it was fed into a computer program that tracked my progress and issued predictions about my ultimate capabilities.
After a few months, the scientists running the project had some bad news. The computer program didn’t think I was fully emptying the tank of my “anaerobic work capacity,” even in my hardest workouts. So they assigned me a workout of 15 times a 400-meter sprint and asked me to get serious. With the digital eyes of the mega-corporation tracking my every move, and my training partners egging me on, I threw down a tougher workout than I’d done in over a decade (I’m 42). I live just over a mile from the park where I did the workout, and I had trouble jogging home afterward.
The funny thing: if you’d asked me a few weeks earlier whether I was holding anything in reserve during my workouts, I’d have sworn that I wasn’t. But the kick in the pants from Nike’s supercomputer (combined with my secret desire to impress the Breaking2 team so much that they would call me up to the big leagues for a crack at the two-hour marathon) broke down my illusions. It’s something I should have known, because I’ve spent the last nine years researching this new book Ben mentioned above, and the biggest takeaway from all that research is that our ultimate limits are nearly always dictated by the brain, not the body. That’s the message I encountered over and over again, whether I was looking into the exploits of freedivers, ultramarathoners, or the famous tales of bystanders lifting cars off of trapped children.
Not convinced? Here are five of the key pieces of evidence that convinced me that physical limits are controlled your brain, and three ways you can change those limits.
5 Things That Convinced Me Physical Limits Are Controlled By Your Brain
It's all in your head because…
1. Subliminal messages can enhance your endurance.
In this British study by researcher Samuele Marcora in 2014, cyclists completed a pair of routine time-to-exhaustion tests on stationary bikes. What they didn’t know is that images of smiling or frowning faces were being flashed on the wall in front of them, in totally imperceptible 16-millisecond bursts. When they were shown smiling faces, they lasted 12 percent longer on the test.
Exactly why smiling faces boost your endurance is still up for debate. Marcora believes that seeing smiles subtly changes your brain’s perception of how hard your muscles are working. But in a sense, the mechanism is beside the point. If seeing smiling faces changes your physical limits, that means it was your brain calling the shots all along—especially if you’re not even aware you saw the smiling faces, which rules out a placebo effect.
2. Freedivers can hold their breath for over 11 minutes.
The world record for breath-holding is 11 minutes and 35 seconds. That’s amazing, but you might assume that it’s because the record-holder is a physical freak. It’s more complex than that, though. Most of us give up on breath-holds when our breathing muscles start convulsing, which forces you to breathe against your will. That happens when carbon dioxide levels in your blood get too high, not when you run out of oxygen. But freedivers essentially learn to ignore that hard-wired warning system: they can hold their breath until they literally pass out from lack of oxygen.
I recently had a chance to chat with Brandon Hendrickson, who set the American breath-holding record of 8:35 last year. He told me that the “involuntary breathing movements,” which signal your apparent physical limits, started after about four minutes for him. So his actual physical limits are roughly double the limits that his brain and central nervous system try to impose on him. That’s a huge discrepancy.
Note from Ben: I'm personally quite interested in free diving and also enjoy myself some good spearfishing. Here are a few podcasts that I've done on free diving which you might find interesting:
3. Heat is worse when you know it’s hot.
Don’t get me wrong: extreme heat will slow you down and can be seriously dangerous if you develop heat exhaustion or heat stroke. But its effects aren’t quite as straightforward as they seem. In a heat chamber study back in 2012, cyclists performed better in 89-degree Fahrenheit heat when the thermometers in the room were rigged to falsely display only 79 degrees. Heat is real, but its negative effects are partly the result of our own expectations.
That’s why, if you go for a run on a hot day, you’ll be slower than usual right from the start, long before your muscles or core have had a chance to heat up. You don’t slow down because your body is overheating; you slow down (initially, at least) because your brain wants to prevent you from overheating.
Note from Ben: I personally tried to hack the heat at Ironman World Championships by using a lightweight body cooling vest, arm-cooling sleeves
4. Alberto Salazar (maybe) had hypothermia.
On a related note, this was the probably the most surprising detail I came across during all my research. The 1982 Boston Marathon, better remembered as the “Duel in the Sun,” featured an amazing battle between Salazar and Dick Beardsley. Salazar won, but he then collapsed and had to be taken to the medical tent, where he received 6 liters of IV fluids—yet another example, according to conventional wisdom, of the dangerous link between not drinking enough and developing heat stroke.
The missing detail in this story? His body temperature was measured in the medical tent as 88 degrees Fahrenheit, 10 degrees below normal. This was an oral measurement, not using a rectal thermometer, so it’s not clear what his core temperature was, but he clearly didn’t have heat stroke. Salazar was a famously tough racer: he had a sign posted on his bedroom wall that said: “You will never be broken again.” His collapses had as much to do with his mental ability to push his own limits as it did with his sweat rate.
Note from Ben: For more on the hydration controversy check out this interview with Dr. Tim Noakes on how we're being manipulated by the sports drink industry and what we can do about it.
5. Mental fatigue makes you physically tired.
Intuitively, it seems kind of obvious that if you have a long and stressful day at work, you’re not going to have a great session at the gym. But that link is even tighter than you might realize. In another study by Samuele Marcora, subjects had to sit at a desk and play an extremely simple computer “game”: shapes or letters flash on the screen, and you press a button depending on which shape or letter it is. It’s really easy—you just have to pay attention. Amazingly, after doing this for just 90 minutes, the subjects reached exhaustion 15 percent sooner in an all-out cycling test. When your brain is even a little bit tired, your physical limits shrink.
The implications of this study are extremely wide-ranging. One of Marcora’s ideas is to use this method as a form of “brain endurance training,” using repeated mental fatigue to build mental (and thus physical) endurance. He’s done some pilot studies funded by the British military, and the results are impressive. The downside? I’ve tried it, and frankly, I’d rather run for three hours than do half-an-hour of those mind-numbing computer games. A more immediate takeaway is that you should incorporate a “mental taper” before important races, presentations, and other events. If you’re running a marathon, don’t do your taxes the day before.
Hopefully, those five points give you a sense of why I’m convinced that physical limits are dictated, at least in part, by the brain. With that in mind, are there ways to take advantage of this knowledge?
In short, yes.
3 Ways To Change Your Brain's Limits
1. Zap your brain.
The most direct way to alter your brain’s limits is to alter how the neurons themselves work. Trickling a weak electric current between two electrodes on your scalp makes the individual neurons slightly more likely to fire (or less likely, if you run the current in the opposite direction) for about an hour afterwards. The technique, which is known as transcranial direct-current stimulation, has sparked a huge pile of research in recent years, with lots of conflicting results and overhyped findings. But there’s mounting evidence that applying current to the motor cortex, which is where signals to your muscles originate, really can make exercise feel easier. And if it feels easier, you can go harder for longer.
I’ll throw in two quick caveats.
First, getting this technique to work seems to be extremely finicky. There’s a commercial brain stimulation device on the market from Halo Neuroscience, but personally, I’m still pretty skeptical that the device is really able to replicate what happens in the lab under controlled conditions, and they haven’t demonstrated its effectiveness in any published studies. Second, on a totally personal note, I have some misgivings about whether this should be allowed in sports. Put it this way: when my daughters are old enough to start competing, I hope brain zapping isn’t a standard part of the high-school athletic program.
Caveats aside, though, I’m still amazed that this technique actually seems to work.
I know, I know. I can’t believe I’m making such a feeble and clichéd recommendation either. When I was in Italy covering the Breaking2 project, one of the big topics of conversation was how Eliud Kipchoge kept smiling during the painful final miles of his 2:00:25 race. “I don’t run with my legs. I run with my heart and mind,” he told SI’s Chris Chavez. “When you smile and you’re happy, you can trigger the mind to feel your legs.”
I didn’t pay much attention to Kipchoge’s touchy-feely theories… until the science started to back it up. Last fall, a study showed that telling runners to smile made them roughly 2 percent more efficient, meaning they burned 2 percent less energy to run at the same pace. Smiling helped the runners relax, and it may also subtly alter how the brain perceives the signals from the rest of the body—much like the smiley faces in Samuele Marcora’s subliminal experiment. Personally, I’m not a big smiler during exercise—but I’ve started being much more aware of the opposite when I’m making a big effort grimace. That can’t help, and it’s easy to change once you’re aware of it.
3. Master your internal monologue.
This is another one of those pieces of conventional wisdom that I was always skeptical about. Back in college, we had a sports psychologist working with the track team who taught about self-talk. But we laughed it off—none of us really thought it would work. In the last few years, though, several studies have shown under lab conditions that learning to replace negative self-talk (“This hurts so much! I can’t keep this pace going!”) with positive self-talk (“You’re ready for this. Keep pushing!”) really works. In one study, it improved cycling endurance from 8 minutes to 11 minutes—and, more intriguingly, it enabled the cyclists to push their core temperature a half-degree higher. Changing their internal monologue allowed them to dig deeper into their physiological reserves.
The big takeaway from the self-talk research is that you have the ability to influence how your brain interprets the signals from everywhere else in your body—the pounding heart, the aching legs, the labored breathing, and so on. And that, in turn, helps determine just how far your body is able to push. There’s still plenty of debate among scientists about exactly how the brain regulates our physical limits, but the overall message is clear…
…sometimes, it really is all in your head.
It's Ben again and…
…wow! Fascinating stuff, eh?
Do you have questions, thoughts or feedback for Alex or me?
Leave your comments below and one of us will reply! And be sure to grab the book Endure: Mind, Body, and the Curiously Elastic Limits of Human Performance if you want plenty more. In my opinion, this book is for anyone who exercises, and not just hardcore endurance athletes. Enjoy.