What extreme athletes learn when they push to the limits

In September of 2019, Sarah Thomas—a then-37-year-old marathon swimmer from Colorado who was still recovering from breast cancer—pulled off one of the most remarkable feats of athletic endurance in modern history. 

Thomas began by swimming from England to France. Upon arriving, she touched a rock, and, a few moments later, turned around and swam back to England, whereupon she touched a seawall and again returned to the water. After arriving back in France, some 40 hours after she began her swim, Thomas—by now sleep-deprived, swollen from sea salt, stomach in open revolt—did something that’s hard to imagine: She returned to the cool, dark water and made for England. The next day, more than 54 hours after beginning her swim, Thomas arrived on the shore of Dover, bloated, caked in Desitin, bleary-eyed, and barely able to stand—the first person in history to complete a four-way crossing of the English Channel. 

If anyone can explain the psychology of endurance, it should be Thomas. Only, as it turns out, explaining it is far different from living it. 

When people think of endurance sports, they often picture ultramarathons, those sufferfests where competitors hurtle on through day and night, downing carbohydrate gels, taking five-minute power naps, and grinding away until toenails fall off.

To make it through, runners turn to different strategies. Ultramarathon champion Courtney Dauwalter, a former science teacher in Colorado, famously enters what she calls the “Pain Cave,” envisioning an actual cave and herself in a hard hat, wielding a chisel, “going to town, trying to make it a dust pile while I am in there.” Scott Jurek focuses on detaching from negative thoughts and embracing a flow state.

Then there are the sustained feats of endurance, like the one attempted by the aptly named “marathon monks” of Mount Hiei near Kyoto, Japan, who run the equivalent of 1,000 marathons in 1,000 days in a quest to reach enlightenment. Those who succeed are honored as Daigyōman Ajari, or “Saintly Master of the Highest Practice,” revered for their extraordinary discipline and spiritual insight.

But the marathons aren’t even the hardest part. In one part of the trial, known as the doiri, monks must sit in constant prayer for nearly 10 days without food, water, or sleep, all under round-the-clock watch. During this phase, the monks say, the line between life and death becomes paper-thin.

Battling the depths

Wanting to push your limits is one thing. Getting your body to comply is another, given that millennia of evolution have instilled a host of built-in biological kill switches and fail-safes.

When I went searching for information, one of the first names that showed up was Tim Noakes. A South African sports scientist, Noakes coined the idea of a “central governor,” a subconscious control center that monitors the body’s internal signals and steps in to slow us down before we reach true physical danger. According to Noakes, we almost always stop well before we’re actually out of energy; the brain’s job is to protect us from ourselves. Noakes argued that this central governor acts preemptively—long before metabolic catastrophe strikes—limiting effort in anticipation of damage. 

If this sounds like a useful trait, well, most of the time, it is! It’s what protects us from injury and calamity. Unless, that is, you are purposefully trying to push beyond those limits. Doing so requires finding a way to bypass, or override, that central governor, and as it happens, swimming provides a revealing canvas for exploring this quest.

Unlike running, climbing, and cycling, which offer external stimuli in the form of terrain, scenery, aid stations, and other competitors, distance swimming is radically internal. You can hear virtually nothing. You stare down into murk for hours—days—at a time. The sensory deprivation can be overwhelming.

The earliest marathon swimmers had no issue overriding their regulator because they already risked their lives with each swim (unlike in running, you can’t just stop and walk if you get tired in the middle of the ocean). Walk the beach in Dover, and you’ll come across a statue of Matthew Webb, the first person to successfully cross the Channel unaided. A swaggering, barrel-shaped British merchant seaman, Webb pulled it off in 1875, when shipwrecks and deaths at sea remained common. As a former sailor, he understood the risk intimately. While working on a Cunard Line ship sailing between New York and Liverpool, Webb dove in when another sailor fell overboard. Though he couldn’t save the man, the selfless act drew acclaim, and Webb won a prize from the Society for the Recovery of Persons Apparently Drowned.

For his Channel attempt, Webb wore a red swimming costume and slathered himself in porpoise oil to guard against the cold. He breaststroked the entire 21-mile distance, fueling himself with beef tea, cod liver oil, and regular swigs of brandy and other “energy drinks” handed to him by crewmen in a support boat. 

In the end, it took Webb nearly 22 hours to complete the swim, during which he dodged jellyfish, tides, and creeping hallucinations. By the time he staggered ashore in Calais, barely able to stand, he had become an international sensation, and he lived out the rest of his days chasing grander and grander feats in the water until his final stunt—attempting to swim through the whirlpool-ridden rapids below Niagara Falls—proved fatal. His epitaph read, “Nothing Great is Easy,” a fitting summary of the sport he helped launch. Fifty years after Webb, Gertrude Ederle became the first woman to cross the Channel, famously leading to one of the largest ticker-tape parades in the history of New York City. Five decades after her, Lynne Cox showed up as a teenager to set a speed record.

By the time of Sarah Thomas’s four-way attempt, a quartet of swimmers had successfully made a three-way crossing—an American, a Brit, a New Zealander, and in 2015, Australian marathon swimmer Chloë McCardel, who spoke afterward of the long nights of the swim. “It’s at night when the demons come out, those deep insecurities and self-limiting beliefs.” Thomas battled more than most.

When Thomas and I connected via Zoom, she told me that when she first booked her Channel attempt, in 2017, she viewed it as a “retirement swim” of sorts—she was coming off years of open water feats and about to set the world record for the longest continuous, unassisted, and current-neutral swim, in Lake Champlain (an astounding 104.6 miles). Having already crossed the Channel, she now wanted to return and take a run at history. She booked a “tide window” two years out. Only, eight months after booking her slot, she was diagnosed with an aggressive form of breast cancer. Sixteen rounds of chemo, a mastectomy, 25 rounds of radiation. She kept swimming through much of it, dragging herself to the pool between infusions, even when she could barely lift her arms. “It was the one thing that made me feel normal.” By the time of her tide window, in September 2019, her hair had only just grown back.

Normally, Thomas could get in a zone when she swam, lost in her own thoughts—what many open water swimmers call a moving meditation. The longer you’re out there, the quieter everything gets. But after her mastectomy, doctors had put in a tissue expander as a temporary placeholder. Lacking time for another surgery before the Channel, she had to swim with it in. “It’s like having a softball attached to your pec muscle,” she said. “Super uncomfortable.” It also forced her to adjust her stroke, her right arm acting “all wonky.” The result: “I tell people that I remember every single moment of the English Channel because I couldn’t get into that flow state. I was very present, and I did not want to be very present.”

The wisdom of slogging it out

In my conversations and research on endurance, a theme emerged. While the how may be hard to fathom, it’s nonetheless relatively easy to explain. It involves muscle tissue and mantras and feed strategies. The why of it—that’s the trickier part. What draws someone to override the brain’s central ­governor—to push past the point where every system screams for them to stop?

For some, it’s about learning through failure. That’s the idea behind the misogi challenge, or at least the modern interpretation of the Japanese tradition: taking on something hard—say, a marathon swim—in which the odds of success are intentionally set around 50 percent. The premise: by pushing to that limit, we learn the most about ourselves. 

The marathon monks view endurance as a gateway of sorts. The idea is to exhaust body and mind until nothing is left. At that point, as one of the monks explained to a journalist, “When you are nothing, then something, pop, comes up to fill the space.” That “something,” the monk said, is the “vast consciousness that lies below the surface of our lives.”

That manifests differently for different people. Marathon swimmer Elaine Howley told me the story of her first swim to Catalina, off the California coast. “I was terrified when I started,” she said. “You’re launching at like 11 o’clock at night, jumping off a perfectly good boat into the middle of the Pacific. And there’s things with teeth that live here.”

She continued: “And I had just watched some flying fish go by, and they were being chased by sea lions. And then of course my brain goes to what’s chasing the sea lions.” But then she got in the water and caught some bioluminescence. “Every time I put my hand in, I would get Star Wars warp-speed lights off my hands. And it was absolutely mesmerizing.” The lights pulled her out of her fear and “into a space where I was like, this is so cool. The world is a pretty amazing place.” She paused. “And for me, it’s such a good metaphor for life. I mean, life is hard. Life sucks sometimes, but then you get these moments of just sheer wonder and awe and beauty, and it’s like, OK, I can keep slogging.”

Or, put another way, the more hard sh*t you do, the easier it is to do hard sh*t.

Thomas agreed. During the four-way crossing, saltwater blasted up her nose and down her throat as she fought the current, too fatigued to breathe properly. She nailed a jellyfish with her face. And when she faltered during the long nights, her friend Howley jumped in to swim alongside her, yelling: “We don’t make decisions in the dark.” The idea: never do something rash in your lowest moments. “You have to give me until sunrise before you quit,” Howley said. “Then see how you feel.” That became Thomas’s internal motivation: This sucks right now, but the sun will come up in a few hours, and we’ll be fine.

She pushed through, the sun rose, then went down again, then rose again. When she hit land in England, just after dawn, 54 hours after launching, a crowd awaited. Though the point-to-point swim is technically 80 miles, due to current and tides, she’d actually covered 130. She celebrated with glorious handfuls of peanut M&M’s.