PHOTOGRAPH BY BERTRAND DESPREZ / AGENCE VU

What are they thinking? Whatever your opinions about running, that is a reasonable question to ask, not just rhetorically but also literally, about the more than fifty thousand people who ran the New York City Marathon on Sunday. Like most major races these days, the marathon has become a serious spectator sport, with more than two million onlookers crowding the city’s sidewalks, and millions more watching on TV. Yet the essence of the experience remains invisible. Runners may smile or cry or limp or double over or raise their fists like Rocky, but these are crude proxies for what is going on in their minds during those 26.2 miles between the Verrazano-Narrows Bridge and the finish line, in Central Park.

Two hours if you’re Meb Keflezighi, six if you’re Joe Schmo: with the exception of bike racing, no other sport involves as much time to think as long-distance running. Golf rounds are slow and baseball games borderline endless, but the actual moments of play are comparatively brief and highly focussed; like faster, reflex-reliant sports—basketball, soccer, ice hockey—they do not conduce to abstract thinking. In endurance running, by contrast, one thinks at great length while doing the activity. To run five or ten or twenty-six miles is, as much as anything else, to engage in a sustained way with the deep strangeness that is the human mind.

Not least because of that deep strangeness (though also thanks to various technical limitations), the mind has thus far proved only moderately amenable to scientific study. Nonetheless, researchers have lately turned to science to try to figure out what runners think about while they run. In a study published earlier this year in the International Journal of Sport and Exercise Psychology, the sports psychologist Ashley Samson and three colleagues clipped microphones onto ten distance runners and asked them to narrate their thought process during a run. Afterward, the researchers transcribed those monologues, identified the thoughts they contained, and divvied them up into three categories: Pace and Distance, Pain and Discomfort, and Environment.

The results make for entertaining, if not exactly convincing, reading. The (notably tiny) group of runners spent most of their time thinking about pace and distance—translated cynically, about how hard it was to move at their desired speed (“Come on, keep the stride going, bro”) and about how soon they could stop (“Come on, you have enough energy for a mile and a half”). But, after that, the runners mostly thought about how miserable it was to run. “While all the participants had periods during their run where they appeared to be comfortable and thinking about other things,” the researchers wrote, “pain and discomfort were never far from their thoughts.” Feet went numb, stomachs ached, lungs heaved, exhaustion loomed, hills hurt, heat sapped, vomit threatened; all told, fully a third of runners’ thoughts concerned the downsides of running. The remaining thoughts pertained to the runners’ immediate environment, which the researchers further subdivided: runners had mostly pleasant thoughts about terrain and wildlife, and mostly unpleasant thoughts about weather, traffic, and the other people around them.

Like a fair number of psychological studies, this one confirmed the obvious while simultaneously missing it. Of course runners think about their route, their pace, their pain, and their environment. But what of everything else that routinely surfaces in the mind during a run? The new girlfriend, the professional dilemma, the batteries you need to remember to buy for the smoke detector, what to get your mom for her birthday, the brilliance with which Daveed Diggs plays Thomas Jefferson (if you are listening to the soundtrack to “Hamilton”), the music, the moment (if you are listening to Eminem), the Walter Mitty meanderings into alternate lives: all of this is strangely missing from Samson’s study. The British author Alan Sillitoe got it right in his 1958 short story “The Loneliness of the Long Distance Runner”: “They can spy on us all day to see if we’re … doing our ‘athletics,’ but they can't make an X-ray of our guts to find out what we’re telling ourselves.”

But where the scientists fails, the writer may succeed. “The Loneliness of the Long Distance Runner” may be the most famous story ever written about running, and it does an exceptional job of capturing how the mind of a runner wanders and swerves and expands as the miles unfurl. Its protagonist, a seventeen-year-old known only as Smith, spends his daily morning runs thinking—occasionally about pace and pain and his surroundings, but chiefly about money, moral codes, friendship, his father’s death, the crime that landed him in a juvenile detention center, and how to assert himself over the authorities who are simultaneously keeping him locked up and championing his running career. Smith is a fictional character, of course, so his thought process as he runs is both an invention and, in a sense, a formal convention—a way for Sillitoe to structure his narrative. Yet his story might get closer than Samson’s study to answering the question of what runners think about while running.

The same could be said of stories in general—so far, fiction does a better job of capturing consciousness than any other method ever tried—but, unfortunately, running stories are, at best, uneven. For every Alan Sillitoe there is a Paul Christman, whose 1983 novel, “The Purple Runner,” begins with a blonde in nylon running shorts slowing to a stop. “Arms akimbo, she cocked her hips to rest upon one of her two statuesque legs, breathing deeply to settle the anaerobic debt acquired from her climb.”

Nonfiction about running is arguably better, and indisputably more abundant. Yet despite the explosion in memoirs and training guides (including some that focus on how runners think: “Brain Training for Runners,” “Elite Minds,” “Running with the Mind of Meditation”), very few such books address the mind of the runner in descriptive rather than inspirational or aspirational terms. The most prominent exception is the novelist Haruki Murakami’s “What I Talk About When I Talk About Running,” which manages to be neither inspirational nor aspirational nor descriptive. “What exactly do I think about when I’m running?” Murakami asks. “I don’t have a clue.” He is not describing the slipperiness of conscious thought in the runner’s mind; that is all he has to say. “On cold days I guess I think a little about how cold it is,” he writes. “And about the heat on hot days.”

That kind of banality is vintage Murakami, but it does very poor justice to what other people think about while running, and to the inherently profound nature of the enterprise, which mingles body and mind, pleasure and suffering, self and world. Books that do better justice are rare, but last year a small Southern press published, with near-zero fanfare, an understated little volume that does more than both the current science and the current literature to illuminate the mind mid-run.

Poverty Creek is a meandering stream, edged by wetlands and shaded by Appalachian hardwood, that flows southwest from the continental divide just outside of Blacksburg, Virginia. For nearly ten years, the trail system that surrounds it and shares its name has served as the running route of Thomas Gardner, a professor of literature at Virginia Polytechnic Institute and State University, better known as Virginia Tech. Last year, Gardner published “Poverty Creek Journal” (Tupelo Press), one of the better books about running I’ve read, and the only one to uncover the literary possibilities inside the terse, repetitive, normally unimaginative genre of the running log.

“Poverty Creek Journal” consists of fifty-one entries, beginning on January 6, 2012, and ending on December 30th of that same year. Almost all take the day’s run as their point of departure, and none exceeds a paragraph. Through these constraints, running is simultaneously put in its place—the forty or sixty or ninety minutes Gardner spends each day on his morning runs mirrored in tightly limited lines—and, like a sonnet, permitted to contain everything. Indeed, of the many forms that the book glancingly resembles, one is the sonnet sequence.