Erwan Le Corre seems to defy gravity—and not just because he’s French.

I’m standing close by as the 39-year-old movement coach—shirtless, barefoot, and built like Mikhail Baryshnikov—hops up and grasps a wooden bar lashed eight feet off the ground between two stout maple trees. Le Corre dangles calmly from both arms for a moment before swinging one leg up to the side, hooking it over the beam, and—swoooop—crouching on top of it and looking down at us. The move is so swift and catlike that I’m not quite sure how he did it. A few minutes later, I attempt the same thing, legs scissoring awkwardly until my arms give out and I hit the dirt with a thud, kicking up a cloud of dust.

This is day one—hour one, in fact—of caveman camp: July’s weeklong MovNat Reawakening Workshop, at Summersville Lake Retreat, an RV resort in West Virginia. MovNat, an abbreviation of “Move Naturally,” is the outdoor fitness-and-conditioning business that Le Corre founded in 2008. Our camp—modern dome tents, a fire ring, and a kitchen area covered by a canopy—is set up in a grassy clearing a couple of miles from the lake. Gyms are out; wilderness is in. Instead of weights, we lift rocks, logs, and one another. Hand-to-hand combat is as much a part of the regimen as lying in the grass and watching billowy clouds blow by.

“MovNat is a comprehensive lifestyle,” Le Corre tells us. “It’s about diet and nutrition. It’s about exposure to sunlight and nature. It’s about getting rest. It’s about feeding the mind with healthy insights and positive thoughts.” Le Corre, who relocated to the United States full-time in 2009, founded MovNat on the premise that humans once dashed around untamed landscapes with power and grace, gathering berries, toppling mastodons, and so forth—and that proficiency at such things will help reconnect us to the world in which we evolved. Not only were we born to run, he says, but also to jump, climb trees, swim deep underwater, slog through swamps, stalk prey, and fight off attackers.

“We live like zoo animals!” he continues that morning, pronouncing it “ah-nee-mahls.” It’s an idea Le Corre borrowed from the British zoologist Desmond Morris, author of the 1967 classic The Naked Ape, and it’s central to his worldview: that we are essentially wild creatures ill-suited to desk jobs and processed foods. “We have become divorced from nature, trapped in colorless boxes,” Le Corre says. “We have lost our adaptability, and it’s threatening our health and longevity.”

Clearly, the approach holds some appeal: all five of Le Corre’s $1,700 summer workshops have sold out. I’d worried slightly about the freak factor before arriving, anticipating a clan of wayward hippies and hairy Luddites. But the group is surprisingly normal—and cosmopolitan. Among others, there’s a corporate-recruitment manager from Osaka, Japan; a musician and his wife from London; a journalist from Zürich, Switzerland; two brothers from northern New Jersey; a Web designer from Brooklyn; and a computer programmer from Tallahassee, Florida. Everyone looks reasonably fit and is either barefoot or, like myself, shod in Vibram FiveFingers, the simian-looking foot-gloves.

“When I saw his promotional video, The Workout the World Forgot, I thought, This makes sense,” Richard Carlow, the manager from Japan, tells me when I ask what inspired him to make such a long trip. “I wanted to learn it from the Source.”

The Source is being assisted by Vic Verdier, a 42-year-old former French commando who currently lives in Thailand, where he teaches Krav Maga, the official self-defense system of the Israeli Defense Forces, and other martial arts. The only other staff is Allie Brodeur, 22, an accomplished acro-yogi and poi spinner—and our camp cook.

They make a colorful trio, but it’s Brodeur’s cooking that’s the focus of most of our first day’s conversation. That’s because we’re all being put on a strict version of the paleo diet, as in “Paleolithic,” a pointedly unhedonistic approach to nutrition modeled after the eating habits of our hunter-gatherer forebears. Meat, fruits, veggies, nuts, and certain oils are OK, but grains, dairy, salt, sugar, caffeine, and alcohol are all verboten. Starbucks, I’m reminded on the first morning in camp, didn’t materialize until the Late Neolithic.

By the time I turn in that night, after more exercises and a dinner of gravyless pork ribs and boiled carrots, I’m drained and swan-diving into full detox: woozy, wobbly-kneed, and worried that it’s going to be a very, very long week. I do, at least, find a queen-size air mattress and cotton sheets in my tent. “This isn’t survival school,” Le Corre reassures me. “We want you to be comfortable here.” One great thing about hunter-gatherers, apparently, is how much they love Bed Bath & Beyond.

MOVNAT DRAWS FROM some familiar sources—CrossFit, low-carb diets, barefoot running, martial arts, mud wrestling, Quest for Fire, etc.—but Le Corre’s program occupies a space all its own. If anything, MovNat falls within the concept of “evolutionary fitness,” an increasingly popular trend embraced by a loosely organized but fast-growing global community of health enthusiasts, medical professionals, and athletes. The movement is often lumped under the “paleo” rubric, but it’s more than just a prehistoric way to eat and exercise.

The most fervent paleos prefer raw meat (thankfully, our workshop meals were always cooked), eschew footwear, fast periodically, and entertain themselves by dissing vegetarians—especially vegans, who they believe are misguided about human nutrition. But most paleos are more moderate, embracing the 80/20 rule: don’t despair over the occasional bagel or sundae, as long as you adhere to the diet roughly 80 percent of the time.

The basic tenets of the paleo diet have been kicked around for years, but its watershed moment came in 1985, when an anthropology professor at Emory University named S. Boyd Eaton published “Paleolithic Nutrition: A Consideration of Its Nature and Current Implications” in the New England Journal of Medicine, suggesting that the paleo diet could be a public-health panacea. While the paper made a sizable splash, it wasn’t until Loren Cordain, a professor of exercise science at Colorado State University, came across the piece a couple of years later that the idea began to reach a larger audience. Cordain eventually became the reigning authority on paleo nutrition and, in 2001, published The Paleo Diet.

Interest in the paleo lifestyle sputtered along for a few years, with help from flag bearers like Ray Audette, the author of NeanderThin, and Frank Forencich, author of Exuberant Animal, as well as a few primal-exercise proselytizers, like Art De Vany, a buff eptuagenarian and former economics professor from Los Angeles whom many credit with launching the evolutionary-fitness idea and whose latest book, The New Evolution Diet, is due out this month. But toward the end of the aughts, something curious happened: Cordain’s royalty checks began to fatten up, and The Paleo Diet crept into Amazon.com’s top 100. Cordain attributes much of the book’s sleeper success to Robb Wolf, a former champion power lifter and biochemist who apprenticed with him in 2006.

In the late nineties, Wolf had suffered a series of health problems, including ulcerative colitis, high blood pressure, and depression. “I was augering into the mountainside,” Wolf told me. Two years later, ailments cured by the paleo diet, Wolf discovered CrossFit, the popular strength-and-conditioning system that combines weight lifting, sprinting, and gymnastics. Eventually, Wolf took the paleo message to the greater CrossFit community, speaking often at gyms and events. Word spread with viral intensity, and as CrossFit mushroomed—the brand grew from 13 affiliated gyms in 2005 to 2,200 by 2010—so, too, did paleo’s popularity.

These days, low-carb, high-protein diets are embraced by everyone from professional athletes to suburban moms. While the paleo approach is considerably more holistic than, say, the now disparaged Atkins diet, not everyone is buying it. The influential nutritionist Marion Nestle, for example, has questioned the wisdom of completely eliminating grains and dairy from our table. “It’s never a good idea to restrict food groups unless you have to,” Nestle says. “These foods have been eaten by humans for a long time with much pleasure as well as nutritional value.” Others, like Katharine Milton, a respected anthropologist at UC–Berkeley, argue that paleos’ fundamental presumption—that we have been unable to adapt to relatively new types of foods since the advent of agriculture and animal husbandry—is flawed. Humans, Milton argues, have always, even in Paleolithic times, adjusted to their changing environment, nutritional and otherwise, quite well.

Despite the lack of consensus, by the time I get to caveman camp, premodern diets and exercise are a small but growing phenomenon. NFL veteran John Welbourn preaches the paleo diet to his former teammates on the New England Patriots. Endurance gurus like Joe Friel, who, along with Cordain, co-authored The Paleo Diet for Athletes, urge triathletes to try it. Similarly, books like Christopher McDougal’s Born to Run, about Mexico’s Tarahumara tribe, are inspiring people to run barefoot or nearly barefoot, helping jack sales of Vibram FiveFingers by a factor of five in just the past year. Countless Web sites, books, and blogs have sprung up too, along with a handful of local paleo clubs across the country whose members gather to do things like learn archery and make grass-fed-beef jerky.

AT CAMP, WE FALL INTO a familiar pattern: up by seven, hearty breakfast, some warm-up drills, a skill-building session on barefoot running or proper log-lifting technique, lunch, siesta (or “MovNap”), a combo circuit, a swim in the lake, meaty dinner, and a lecture on topics such as lipid metabolism or the value of vitamin D.

So far, considering there was no fitness test required, attrition has been pretty minimal. A few of us have missed meals because we weren’t feeling well, though some have been hit worse than others. There’s a strict no-snacking policy, and Dave Csonka, the computer programmer from Florida, who’s a buff six-five, has been begging for bananas because his blood sugar keeps crashing. Worse, his arms are covered in poison ivy. On one of our daily 40-minute barefoot hikes to the lake, Oswald Fombrun, one of the brothers from New Jersey, gets nailed just beneath the eye as we dash past a hornet’s nest hidden in some rocks. The hikes have been a favorite part of my day, in which I imagine myself a wily hunter tracking down lunch, until I get stung twice on the arm.

Most of our training takes place in a shady grove near camp, where Verdier and Le Corre have built a temporary outdoor gym, with timbers lashed at different heights between trees, a complement of rocks and logs, several four-by-four balance beams, and a couple of picnic benches for high jumps. Verdier mostly hovers quietly in the background, while Brodeur keeps the food processor and blender humming back at camp.

On occasion, Le Corre will interrupt what we’re doing to demonstrate proper technique or impress us with feats of skill and strength. After a few of us fail to move a massive log, he comes over, levers the tree trunk (which must weigh more than 300 pounds) onto his shoulder, and carries it the 100 yards to camp, where he plunks it by the campfire, dusting the bark off his arm with a theatrical flourish.

Le Corre is tall and tawny—the kind of physique you might expect to find if you waxed the hair off a Neanderthal. Still, for all the hard-bodied exterior and motivational speeches, he’s no drill sergeant. His coaching is seasoned with quasi-mystical declarations, like “Oxygen is an accident, breath is intentional,” and tips, like how listening to more reggae encourages rhythm and flow. At one point, I find him standing in the grass, performing some sort of sun prayer, head bowed, one arm raised to the sky. “I was just having a moment of gratitude,” he says. He owns an iPhone, drives a Land Rover, and, perhaps due to his Frenchness, is comfortable wearing tight black briefs at the lake.

By the third morning, I’m filthy and sunburned and have acquired hundreds of tiny cuts and scratches that sizzle in a glaze of sweat. Even so, my body has (mostly) adjusted to the diet, and I’m feeling surprisingly good as we squirm around on crackling brown grass under a blistering sun, practicing an evasive move that might help us escape an attacker. Le Corre barks that we have become domesticated, that our sterilized and hermetically sealed lives have left us intolerant of nature. “But you can train dirt!” he exclaims, making an oblique reference to the fact that being exposed to grit and germs helps bolster our immune systems.

Not only does exercising outdoors make us more resilient, says Le Corre; it’s also a better conduit for fitness than the typical cardio penance or preacher curls popular at big-box gyms, where waist trimming and biceps bulking are the main motivators. MovNat advances a concept that certain athletics coaches have pushed since the seventies, one that treats the body as a tool for dynamic movement, not a topiary sculpture.

Later that afternoon, after practicing more barefoot running (“Fall forward, catch yourself on the front of your feet”), Le Corre adds a twist to our trip to the lake. Along the way, we have to stop and carry a partner on our backs. I team up with Christoph Zürcher, 44, the journalist from Switzerland, who’s six-two and has about 20 pounds on me. We’re sweaty and shirtless, and I awkwardly hop on his back while he hooks his arms under my legs and starts lumbering forward. “Uuuuugghhhhh,” he groans. “How far are we supposed to go?”

“Switch!” Le Corre shouts after about five minutes, and I stagger down the trail, bent under my crushing Swiss payload. At last we scramble over large rocks and emerge at the lake.

“The more we move, the smarter we become,” Le Corre says as we sprawl on the rocks after our swim. “We’re less stressed when we see green, like leaves and grass.” A motorboat whizzes by, towing a water-skier. “I love technology,” he continues. “I love all the modern conveniences that we have now, but we have to ask: When do we use it, and at what cost?”

LE CORRE GREW UP RUNNING around the fields and forests on the outskirts of Paris. He dabbled with ball sports—soccer, tennis—but hated the rules and boundary lines. At 15, he moved on to karate, quickly surpassing older, more experienced opponents. But he also found karate’s formal protocols and tense competitions too staid and confining.

Then, at age 18, he happened to watch a television show about a 45-year-old Parisian stuntman named Jean Haberey. At one point, Haberey jumped out of a helicopter into an iceberg-strewn ocean wearing only swim trunks. It was the most outrageous thing Le Corre had ever seen—and he wanted to do it, too. A year later, he tracked Haberey down, and for the next seven years he followed him and his other disciples around the French metropolis, playing high-risk games: a “fight club of natural movement,” as Le Corre puts it.

“He was the first guy to take people up onto the roofs of Paris,” Le Corre said. “He also took us down into the underground, always barefoot, with no gear at all, to train people how to move silently like cats through urban obstacles … especially at night, when everyone was asleep.”

Once, Haberey and Le Corre held a sit-up competition while dangling by their legs from a bridge over an eight-lane superhighway. Another time, Le Corre climbed along the transom of a tower crane, legs dangling in the void nearly a hundred feet above the ground. “It was crazy,” Le Corre recalls, “but you just felt so alive.”

Haberey’s urban antics helped kick off the parkour craze, but Le Corre, like most of his followers, eventually grew disillusioned. “I supported him for a while,” Le Corre says, “but it turned into a cult of his personality. It became too dark and underground, all about helping him, not others.”

For a few years, Le Corre delved into endurance sports, competing in Ironman-distance triathlons while supporting himself with odd jobs, including making soap and men’s jewelry. But turning himself into a perpetual-motion machine wasn’t his raison d’être, either. Finally, in 2004, he stumbled upon an online comment about Methode Naturelle, an obscure training manual published in 1912 by Georges Hébert, a French naval officer. The book featured black-and-white photos of robust young men in briefs performing all kinds of primal-movement exercises: jumping, running, swimming, climbing, etc.

“I was like What?! This is exactly what I was doing before, but this guy had given it a name,” says Le Corre. “He had systematized it, and I thought, That’s the way to go.”

Hébert’s motto was “Being strong to be useful,” a concept largely inspired by the defining event of his life. On May 8, 1902, Hébert was stationed on the Sughet, a naval ship just offshore of Saint-Pierre, on the island of Martinique, during the infamous eruption of Mount Pelée. In minutes, the blast flash-fried most of the town’s 30,000 citizens, searing them with pyroclastic ash before burying them in tsunamis of mud. Amid the carnage, Hébert and his shipmates were credited with saving some 700 lives, pulling from the sea scalded men, women, and children, some of whom had been blown hundreds of feet through the air by the blast.

Preparing your body and mind for real-world, life-or-death applications is at the root of MovNat. Our workshop activities (throw a rock, climb a tree) may seem random, but they’re intended to cultivate what Le Corre refers to as “selective tension,” a kinetic reaction in which muscles relax and contract in patterns that help you move efficiently, especially in unpredictable situations. To underscore their practical value, Le Corre would often cite imagined modern-day scenarios during our training. “What if you had to pull someone from a burning building?” he asks one morning. “Or a flood,” Verdier adds. “Sometimes survival comes down to who can run up a flight of stairs and who can’t.”

One afternoon, Le Corre shows me a video on his laptop, basically the director’s cut of The Workout the World Forgot. I recognize a few scenes: Le Corre scrambling through brambles and running on the beach in Corsica. But there’s other, more dramatic stuff in this version. “I can’t put this online for liability reasons,” he says as he appears onscreen jumping, from boulder to boulder, across a raging, flood-swollen river.

In the next scene, as a large wave subsides, Le Corre leaps from a cliff into a frothing sea; it looks as if he’s about to be pulverized into human bouillabaisse. As the next wave arrives, he angles his body and kicks—a subtle, fishy move that lines him up in front of an impossibly narrow opening in the rocks. The wave breaks, but Le Corre rides it like driftwood into the small alcove. He vanishes briefly as the chaotic surf washes over the shore. The water retreats, and there he is, crouched on the rocks, unscathed.

“I’m not trying to show off,” he says, perhaps sensing my disbelief. “I’m just showing you what’s possible.”

TOWARD THE END OF the week, Verdier finally takes center stage. It’s combat time. “The best option is always to get away,” Verdier says. He speaks with a measured calm that reminds me of David Carradine in Kung Fu, a TV series I loved as a kid. “But if we have to fight, we should be ready to fight to the end.” Street battles are “total chaos,” he says. “You’re flooded with adrenaline, and most fights don’t last more than a minute.”

Verdier passes out muay Thai strike pads, and we take turns punching the pad as hard and fast as we can. I team with Fred Fombrun, 26, one of the brothers from New Jersey. Both Fombruns are serious amateur boxers, and Fred’s first punch is so powerful I stagger backwards and almost fall over. It takes all my energy to keep my feet during his flurry. My own assault is considerably less impressive; at one point, I notice Fred checking messages on his iPhone while I hammer away at the pad.

After fight class, we adjourn to camp, where Brodeur has lunch waiting. Spaghetti! Oh. No. It’s zucchini, shredded to look like spaghetti: zughetti! Still, the veggies are dressed with raw campari tomatoes, sun-dried tomatoes, fresh basil, garlic, oregano, olive oil, and cracked black pepper—and it’s delicious. I’m famished, and I gulp it down like a starved coyote, shamelessly licking the sauce from the bottom of my plate.

Despite my frequent anti-paleo cravings (the movie version of which I’m calling Quest for Fritos), I feel great. My skin feels thicker, my sunburn has faded into a honey-wheat sheen that it hasn’t sported in years, and the soreness in my back and arms has dissipated completely. Only Dave Csonka, the big dude from Florida, seems to still be in decline. In addition to the poison ivy and low-blood-sugar spells, he’s also tweaked his neck. “I’ll be fine,” he says, gamely playing along even though he has to rotate his whole torso to address us individually.

One question we all seem to be pondering is finally asked out loud by Fred Fombrun: “What exactly am I supposed to do when I get back home?” he says. “There aren’t a lotta parks where I live in northern New Jersey.”

Le Corre is working on an answer. In 2009, he met Robb Wolf, the influential CrossFit instructor and The Paleo Solution author, through a mutual friend. Inspired by Wolf’s story and the viral success of CrossFit, Le Corre began hammering out a business plan modeled on it: he hopes to train and certify instructors, who will license the brand for their own gyms or create grown-up outdoor playgrounds like ours. Or both.

I could see the appeal as a general fitness program, especially because Le Corre believes that, if the regimen is intelligently designed, you have to do only a few circuits a week—no more dailies or oppressive dates with the treadmill. “A specialized athlete can improve their game, because training like this helps prevent injury and improve balance,” he says. I figure it will also translate to the things I like to do, like skiing and cycling, because it’s helping my body move the way it was designed to. Best of all, it’s way more fun than doing intervals with a heart-rate monitor.

In the meantime, Le Corre is writing a book about MovNat. He also continues to crisscross the country, hosting one-day clinics, seminars, and other events. In October, he was a VIP guest at New York City’s first annual barefoot run. A few weeks later, he and Wolf traveled to the Johnson Space Center’s Wyle Laboratories to introduce and discuss the benefits of paleo diets and MovNat with NASA.

WORKING OUT On an empty belly, in a “fasted state,” paleos argue, increases production of human growth hormone. So on the last morning, Le Corre has us begin our final, skill-culminating circuit sans breakfast. We begin by walking around the grassy hill near camp, twisting and bending, followed by body-weight squats. Then we drop down and prowl around the hill on all fours. “Scan the horizon,” Le Corre instructs. “Stay low! You don’t want to be seen. Remember: in nature we are ever mindful. Always alert.”

He ratchets up the intensity with push-ups and wheelbarrows, a partner holding your feet, and then tells us to drop to the ground and roll down the hill, like logs. I’m so dizzy by the bottom, I can’t stand up. Nearby, our other Dave, Dave Beretta, a young kid from East Greenwich, Rhode Island, is doubled over, dry-heaving.

Le Corre keeps throttling. We stagger into the wooded training zone for log lifts and stone carrying. Next, it’s balance-beam walking and high jumps. Le Corre throws in some mind games, telling us we’re doing an exercise on a ten count but stopping at eight and then counting backwards or repeating a number over and over: “Seven, seven, seven, seven …”

“Do we function in sets of ten in the wilderness?” he asks. “How do we know how long we will have to do something?”

After more than an hour grinding through the drills, we step up to the high bar that we attempted on the first day. I jump up, hook my leg, and … burst out laughing when I monkey myself on top of the bar. One by one, nearly everyone else, so embarrassingly defeated at the beginning of the week, pulls off the same feat. “See?” Le Corre says, a look of satisfaction on his face. “Progress.”

I leave West Virginia inspired. Back home, I invent circuits in a neighborhood park—sprint barefoot across a field, jump over a bench, crawl on all fours down some stairs—even though I notice dog walkers and parents with small children altering course to avoid me. In the evenings, I cook my girlfriend dinners of grass-fed beef and roasted vegetables, with sliced watermelon for dessert. But it requires a level of dedication, planning, and self-control that I can’t sustain, and soon I’m caught in the undertow of enchiladas and triple cappuccinos and driving a few blocks to the grocery store. My training fades to once a week, then once a month, and finally to watching 10,000 BC on Netflix.

I might have anticipated this while sitting at my gate in the Charleston airport, glumly half-watching a chattering news anchor talk about the Gulf oil spill while pudgy kids trundled by, clutching waffle cones the size of their heads. It dawned on me how each day boils down to a series of decisions centered on convenience and comfort. As I slumped in my chair, sipping water, our final morning in camp already felt distant and dim.

After the last day’s circuit ended, we followed Le Corre down a game trail, deep into the woods. We weren’t allowed to talk and had to move as quickly and quietly as possible. It started to rain, and soon we were not only sweaty but soaked and spackled with forest grit. At one point, Le Corre dropped down on all fours, and we did the same. Crawling down the trail, I crunched over some thorns but didn’t feel a thing.

Eventually, we came to a small, fecund amphitheater, at the center of which was a dark bog, maybe 20 feet in diameter. The air was ripe with the smell of moss and ammonia, and the foliage flicked and glistened neon green. For the first time in 20 minutes, Le Corre finally spoke. Wearing only shorts and a dark-green bandanna, and streaked with mud as if someone had outlined his muscles with a black magic marker, he looked downright feral. “Adaptability is the holy grail of MovNat,” he told us. “This is what we have done throughout human history. But we have lost touch with the world that created us.”

With that, he charged across the swampy black hole, sinking instantly up to his waist but diving his arms and chest into the muck and thrashing his way to the other side in one sustained, growling effort.

The rest of us stood there dumbstruck, a couple of people shaking their heads while Le Corre beckoned from the other side. Finally, one by one, we splashed across to join him. And then, as if to underscore the fact that, yes, we had at last reawakened and it wasn’t so bad, we slogged across the bog again—not once, but twice.