UELI STECK took a deep breath and stared up at the north face of the Eiger, the infamous 5,900-foot wall of fractured limestone and ice, high in the Bernese Alps, that has killed at least 64 people since climbers first started taking it on in 1935. Soon he’d be dangling thousands of feet off the ground from its icy, rounded holds, with nothing to stop a fall. Yet Steck was calm and focused; the nervousness sloughed from his shoulders like spindrift.

The Swiss, then 31, gazed at the far side of the valley that rolls out from the Eiger’s sprawling base, where a weak winter light was inching across the pastures. Up here there was no warmth or sun, which was good. One rock, breaking free from the ice and falling at the wrong time, could kill him instantly, but the cold kept the Nordwand glued together. Steck grabbed his ice tools, started two stopwatches, and exploded up the mountain.

His arms and legs hammered the snow on the 40-to-50-degree slopes at the beginning of the Heckmair Route, the classic, ambling line set in 1938 during the first ascent of the north face, by a German-Austrian team. Steck had never felt so dialed as he did on that February day in 2008. His five-foot-eight frame was wiry with muscle. He’d practiced climbing steep cliffs using only the thinnest of holds, with no rope or partner to catch a mistake. His gear was minimal and precise: an ice screw, four carabiners, a quickdraw, and a hundred feet of cord, which he could use to rappel down if things really got grim.

When the weather holds, most climbers need about three days to do the Heckmair. But a year earlier, in 2007, Steck had shown that it could be completed in less than four hours when he smashed the old record by 47 minutes, with a time of 3:54. Still, something nagged at him. Steck had retraced other people’s steps to avoid the exhausting work of breaking trail on the snowy sections, and he’d relied on climbing gear to aid his ascent through tricky spots—no-no’s to a free-climbing purist. Max Steck, Ueli’s coppersmith father, had taught him never to half-ass anything, but Steck began to believe he’d done exactly that. “I was just faster than the others,” he told me recently with a shrug. “I wanted to reach the limit.”

That’s what this second Eiger speed attempt was all about. Steck had waited for a storm to fill in the footsteps and coat the face with new ice, and this time he would free-solo the whole route with only axes and crampons to keep himself pinned to the wall. He had hired a coach and physical therapist from Switzerland’s top Olympic facility to create a fitness program designed to get him up big Alpine faces as quickly as possible. The training went far beyond what most mountaineers are willing to endure—some 1,200 hours of murderous workouts a year. How could he not be faster this time?

Thirty-nine minutes into the climb, about a quarter of the way up, Steck reached the start of the first crux, a vertical dihedral called Difficult Crack, and noticed that he was ten minutes behind his 2007 record pace. Here, with thin holds covered in snow, Steck would need steady hands, but his heart rate was way too high, making him uncoordinated and clumsy. He paused like a biathlete, reined in his pulse, and went for it. Somehow he gained speed, scaling 180 feet of glazed 5.7 limestone in just four minutes.

Most would find the exposure nauseating, but Steck kept on, blowing across the dizzying, icy slab of the Hinterstoisser traverse in less than a minute. Over the Flat Iron, through the White Spider—the mountain’s legendary features fell behind him like stripes on the autobahn. At last he reached the summit ridge, an airy blade of snow that he ran across in crampons. Soon there was no more up.

Steck looked at his watches. One read 02:47:33, the other 02:47:34.

Could it be? He’d broken his own record by 67 minutes. His lungs burned and his body ached, but Steck sensed that he still hadn’t reached his limit. So he came down, ate some spaghetti, and started climbing the damned mountain all over again.

IN THE YEARS SINCE Steck’s Eiger climb, he’s become famous in both Europe and (to a lesser extent) the United States, where he’s known to many climbers as the Swiss Machine, thanks to a 2010 Sender Films production of the same name. Steck wouldn’t make it to the top on his second Eiger attempt that day—he’d turn around, depleted, 1,500 feet up an easier route—but the next winter he went on to climb the Alps’ two other great north faces in record time: the Grandes Jorasses near Chamonix fell in 2:21 (besting the old mark by four and a half hours), and the Matterhorn went in a farcical 1:56 (cutting the record almost in half). For both climbs, Steck (pronounced schteck) simply walked up and started—no practice, no ropes—so both were on-sight free solos, the riskiest type of climbing there is. Who else but a man-bot could do that?

Too bad Steck hates his nickname. “No one in Switzerland knows me as the Swiss Machine, and that’s good, because I don’t like it,” he says. “For Swiss people, this would be very unsympathisch.” Not very nice.

It’s July 2011, about a year since The Swiss Machine came out, and Steck is standing inside a packed afternoon train cranking its way down toward Grindelwald, a village at the base of the Eiger. He has a shock of chestnut hair and a big grin, and he’s decked out in running gear, having spent most of the day sprinting along a ridge, filming an Audi commercial with the mountain as a backdrop. I’m here to spend a week with him as he eases back into training for another expedition to Nepal, this time to climb new routes up the north faces of three 6,000-meter mountains: Ama Dablam, Tawoche, and Cholatse. For many passengers, it’s as if a movie star just came aboard.

“Ueli Steck! Fastest man on the Eiger!” a man shouts, throwing up his arms. “What you do is just incredible!” People begin to stare.

“We need your picture!” the man says, fumbling with his lens cap. Steck turns to pose, but two girls tap him from behind to ask for his autograph. “This happens all the time,” he says. “I can’t disappear.”

Steck is usually friendly with his fans, and he’s certainly not some emotionless, mission-bound cyborg immune to pain and fear. In fact, he’s good at what he does because he’s afraid—even insecure at times—so he overcompensates by being so physically and mentally prepared that he’s ready for just about any surprise. Whether it’s training, climbing, or sanding wood in his occasional job as a carpenter, Steck is such a nitpicker for quality and precision that to an outsider he can seem like a parody of a control freak. But that’s just Steck being Swiss, a culture I know well from having lived and worked in Switzerland twice, the last time from 2008 to 2011. In this most orderly of nations, there’s a proper way to do everything, right down to when you can flush the potty. (Never after 10 p.m.)

However one views Steck, the odd thing is that his days of daring solo speed ascents may already be winding down, in part because he promised his wife, Nicole, an avid amateur climber, that he wouldn’t venture out alone anymore. “The goal is not to solo,” he clarifies, rather evasively, when I ask if he’s planning to keep his word. “Of course, it is possible to move fast in alpine style also with a partner. I just need the right partner.”

That’s no easy job to fill. Consider Project Himalaya, Steck’s grand effort last spring, sponsored by Mountain Hardwear, to complete fast, alpine-style ascents on not one, not two, but three 8,000-meter Himalayan peaks, including Mount Everest, in a single season, with partners but without using bottled oxygen. The concept alone was unprecedented. “People can spend weeks and weeks just trying to get up one peak,” says American mountaineer Steve House, a fervent advocate of fast-and-light ascents.

Don Bowie, an accomplished pro climber from Bishop, California, joined Steck in Nepal last April for a shot at the steep southwest face of 26,289-foot Shishapangma. But when Bowie, then 41, decided he wasn’t sufficiently acclimatized, Steck broke his promise and raced up the peak alone, in just 10.5 hours. He said he hadn’t meant to go alone, but conditions were good, so he did. “This is not really a solo,” he wrote on his blog in April. “I will let [my wife] know that I summited with a bunch of flowers.”

Eighteen days later, with Bowie feeling better, the two knocked off 26,906-foot Cho Oyu in less than 24 hours, from a spot low on the mountain. Steck had stomach cramps the whole way but kept pace, thanks to a few sips of Coca-Cola stashed in his jacket.

“It was nice not to have to wait for him,” Bowie deadpanned over the phone. “Ueli’s so strong at lower elevations, but then it just does not diminish the higher he goes. He’s strong no matter what.”

Eric Plantenberg and Scott Patch got a taste of that in May when they saw Steck in action on Everest, the final climb of the three. The two American mountaineers were descending from the summit on the Tibet side when they spied a man who was limping badly on his way down. They didn’t know it was Steck, who once again was climbing alone after extreme cold had turned Bowie around at roughly 26,600 feet. Just 45 minutes shy of the summit, Steck had turned around, too, his feet so cold that they felt like blocks of wood. Plantenberg thought the mystery climber could have been in trouble, so he and Patch tore after him, ready to help.

“Then he starts to put this massive distance between us, and next thing we know this limping guy is out of sight, just gone,” Plantenberg recalls. “Patch, who was on a pretty low flow of oxygen, stopped chasing after him and looked back at me like, What the fuck?”

IT'S HARD TO IMAGINE that kind of willpower. After so much training, hope, and work, there you are, minutes away from pulling off your dream, and you can’t. But you could! If you took one sweet hit through an oxygen mask, your sticky, viscous blood would thin, springing your feet back to life.

Nope. “That’s bullshit,” Steck says when I suggest the possibility. “I don’t cheat.”

A few days have passed since the Audi commercial. I’ve met Steck in Lauterbrunnen, a clutch of tidy chalets tucked in a magnificent granite valley. Today’s plan: go for a run. The train platforms are buzzing with tourists when I see Steck bounding toward me in a blue zip-up jersey and black shorts that reveal enormous thighs twitching like high-strung huskies. His white socks are yanked up to his knees, topping off a potent blend of Euro badass and dweeb.

“Today, I keep it easy,” he says as we board a 9:13 train and glide up through the forests over the valley. “Easy” means a five-mile trail run up 2,600 vertical feet from the village of Wengen to the Kleine Scheidegg pass. Steck clips a pedometer to his shoelaces, adjusts his heart-rate monitor, and, at 9:27 precisely, starts his run.

I know I can’t keep pace, so I ride the train farther up the mountain to a wide trail that offers a shortcut to the same pass. My watch reads 9:54 as I set out, pretty sure Steck is still going to beat me.

I’ve hiked this trail countless times, and every time I still trip over my own jaw. Five-hundred-foot-high waterfalls scream off icy blue glaciers. Lupine blossoms stand three feet high on either side of the path. There’s so much Swissiness, it all seems fake. Training like hell wouldn’t be so bad here.

Not that Steck will be admiring any of it. “I have to concentrate,” he grumbled earlier. “You have to focus on making sure that every muscle is pulling. Running just to run doesn’t do anything.”

I beat Steck to the pass (yes!) and celebrate at a restaurant with a beer, a sausage, and another beer. “That’s disgusting,” Steck says when he arrives at 11:17, about 45 minutes behind me. “I hate all that heavy Swiss food.” He orders a salad and a blue-label Rivella, a popular Swiss soft drink made with milk serum, this one sugar-free, and nibbles away like he’s barely broken a sweat.

Steck, of course, is not alone in what he does. In 2010, big-wall climber Alex Honnold broke solo speed-climbing records on the Nose on El Capitan and the northwest face of Half Dome by climbing them back to back in just over 11 hours. Austrian Christian Stangl—later disgraced by his false claim that he’d successfully climbed K2—banged out the Seven Summits in less than 59 hours combined, finishing in 2007. But Steck is a mutant combination of the finest climbers out there, past and present. He has Reinhold Messner’s high-altitude endurance and, like Honnold, can climb 5.13 without a rope. Perhaps most important, he has the brains and prudence of mountaineer Ed Viesturs—known for his obsession with safety—who calls Steck “world-class in what he does.”

While genetics certainly play a role in shaping Steck’s abilities—his long arms place him high on the ape-man scale—his fitness mainly comes from the insane workouts designed by Simon Trachsel, his personal trainer and a physical therapist at the Swiss Olympic Medical Center.

Back in 2007, right about the time Steck dropped Eiger bomb eins, he decided that, if he truly was to reach his own limits, he’d need the help of a top-notch coach. Problem with that: there isn’t a lot of sports-performance research out there on mountaineering, let alone speed climbing or free soloing.

“With cross-country skiers or cyclists, you know exactly what the course is and you have these known systems that you can use to prepare an athlete for the race and gauge his progress along the way,” Trachsel told me when we met one afternoon in Bern. “With Ueli, we are talking mountains. This was new ground.”

At first Trachsel just tidied up Steck’s existing workouts, for example, by grouping endurance with endurance and strength with strength. “Like sorting black stones from white ones,” he says. After three months, the results were shocking. Steck could run laps up a hill near his home in 33 minutes, down from 37, a 10 percent improvement from the simplest of tweaks. “You don’t get the chance very often to work with a top athlete who has so much room to improve,” Trachsel says. “This was very exciting for me.”

Trachsel started making his new pet suffer, turning to research in running and nordic skiing to create a tailored program. There are short runs, long runs, intervals, weight training, rock climbing, stretches, and even sleep analysis to pinpoint muscle recovery times. All the while, Trachsel is studying heart-rate data, times, and distances that Steck feeds into a database. During intense training periods, Steck is back in the lab every two months, strapped to more machines. As a result, he knows exactly how long he can hang on to a tiny nub or whether he has the reserves to push through a difficult spot.

“It’s all very logical for Ueli,” Trachsel says. “His fitness is his security.”

Maybe so, but the intensity of the workouts has raised eyebrows among some of Trachsel’s colleagues, who’ve warned that Steck is destined for injury. At one point, Trachsel had Steck running three laps up a peak near his home—for 18,000 feet of vertical gain. Steck did all three laps in about five hours total, several times a week. I ask him if he ever thinks Trachsel might be pushing him too hard.

“No,” he says. “Simon slows me down.”

NOT SURPRISINGLY, Steck has a hard time relaxing. He’s learned to take a few minutes to visualize things that help him feel calm and focused—imagining easy moves on climbs, say. If he could be any animal, it would be a cat. “A lazy, fat one,” he says. Comic books are great, too. During downtime last spring on Nepal’s 20,075-foot Lobuche Peak, Steck dived into an issue of Donald Duck. “This guy is really funny,” he says.

Steck can be funny, too. Watch him give a talk and he comes across as an enthusiastic and entertaining speaker. But, like most Swiss, he draws a firm line between work and play, and no matter how much I try to blur the two Steck sees me as just another potentially troublesome hack who’s eager to invade his “islands” of privacy. I’ve been ordered not to contact Nicole or his family, which irks me.

“It’s just conversation!” I say.

“No go,” he says, and that’s that.

Fortunately, Nicole is off climbing in France, so one day the shields are lifted and I’m welcomed into the 200-year-old chalet they rent off Lake Brienz. It’s cozy inside, with a low ceiling and towels hanging in a back room stuffed with bins of bolts, axes, and ropes. A large photograph of the Eiger hangs on a wall in the living room, where warped windows look out on a top-trim Audi Quattro parked in the driveway. The German car company gives Steck a new one every year to drive for free. I’m too polite to ask what he earns, but from the looks of things the Stecks are solidly middle-class. “I never expected to make a living from climbing,” Steck says, “but it got to the point where I either had to get a job or start trying to make some real money from it. I didn’t want to be 45 and a dirtbag.”

Steck grew up the youngest of three brothers in the Emmental, an idyllic valley north of Interlaken. When he was 12, a friend of his father’s named Fritz Morgenthaler took him on his first climb, up several 5.7 pitches on a karst ridge called the Schrattenfluh.

“Fritz was old-school,” Steck says. “He threw me on lead right away. I thought it was normal to climb 20 meters with just two pitons and instructions not to fall.” A soloist was born. From then on, Steck has always climbed easy stuff without a rope.

At 18, Steck tackled his first real test, the north face of the Eiger, doing the Heckmair Route in a day and a half. By 21 he was racing up stiff lines on the Mönch, and in 2004, at 28, he and a partner linked the three north faces of the Mönch, the Eiger, and the Jungfrau in one 25-hour push. Things really picked up after he free-soloed a wildly exposed line called Excalibur—a 750-foot-long 5.10d over Wenden, Switzerland.

The happy times almost ended in 2007, when Steck had his first brush with death high on the south face of Nepal’s Annapurna, at 26,545 feet the world’s tenth-tallest mountain. One minute he was climbing alone, rope free; the next he was 1,000 feet lower on the face, suffering from a splitting headache and aching all over, but otherwise fine. He has no idea what happened—his best guess is that a loose rock nailed him on his helmet. Months of reflection followed.

“It was important for me to understand whether I was pushing it too hard or whether it had just been bad luck,” Steck says. “I decided in the end it was just bad luck.”

In 2008, Steck returned to climbing with renewed vigor. In addition to his speed records, he and a young Swiss mountain guide, Simon Anthamatten, put up a bold mixed-climbing route on the north face of Nepal’s Tengkampoche—and earned a Piolet d’Or, a prestigious French climbing award. Months later, Steck and Anthamatten garnered worldwide admiration for rushing to the aid of a dying Spanish climber stranded high on Annapurna, even though it meant calling off their own expedition.

Steck considers the rescue a failure—he saved only one of the two climbers—but the mountain-loving Swiss had a new national hero. “In his sport he is the best Swiss, and for a few years now one of the best in the world,” the Basler Zeitung gushed, paying Steck the ultimate compliment by comparing him to Roger Federer.

Steck will never be as famous as the Fed. But within the confines of German-speaking Switzerland, there’s no doubt he’s become a “sausage celebrity”—a Swissism for personalities famous mainly at home. The Swiss Broadcasting Corporation, my old employer, had him reenact parts of his second Eiger climb for a 50-minute special that aired nationwide. He was featured on another national program called SF bi de Lüt, a lifestyles-of-the-Swiss-and-famous show, and then as a celebrity guest in a televised card-game show called Samschtig Jass. He posed for Schweizer Illustrierte, a Swiss celebrity magazine, and had so many people coming to his slide shows that he booked 92 presentations in one year. Corporations began paying him thousands of Swiss francs to hear his message of “Be your best, not better than the rest.” Audi signed him up, as did Scarpa and Suunto. This year, Mountain Hardwear released an entire line of ultralight gear based on Steck’s specs, including jackets without pockets and down suits that fit inside sleeping bags. He even has a signature Swiss Army knife: the lightweight titanium Ueli Steck Special Edition multitool sells for $200 and comes with a wrench to tighten anchor bolts and a file for sharpening ice axes.

“Wow,” Ed Viesturs says when I run some of this boodle by him. “Did you say Audi gives him a car?”

IN CASE IT ISN'T already clear, Switzerland is a sweet place to be a professional climber. The country has only 7.8 million people—fewer than New York City—but nearly all of them can at least visualize what Steck does. “There are great swaths of the U.S. where people don’t even know what climbing is,” says Viesturs. “Think anyone in the Midwest is going to buy an Ed Viesturs chocolate bar?”

Steck knows his appeal won’t last. Eventually he’ll get older and slow down like the rest of us, but for him, getting out of the spotlight will partially be a relief, since things can get a little claustrophobic in the Alpine kingdom. Steck has become fanatical about protecting his privacy, which can come across as strange from a sponsored athlete who strives to be noticed. He’s been known to snap at fans who ask for an autograph if any family members are with him. Rarely will you see a picture of his house.

Inevitably, my attempts to penetrate the Ueli bubble lead to a temper tantrum. More inevitable, perhaps, is that most of it comes from me. One night at the train station in Interlaken, Steck and I are standing in the glow of the platform lights discussing a plan for my last few days. He has a meeting scheduled with Trachsel and then wants to go paragliding. I ask to come along.

“No, no, no! You’re not going to write about that!” he says, palms up and out, as if I just pulled a gun.

“I can’t come and watch?”

“No, I need that for me.”

I promise him I won’t whip out a notebook or take pictures with my iPhone. No.

“If you come, people will judge me,” he says, exasperated.

“Judge you? What are you talking about?”

“You’re a journalist, but you don’t get it,” he snaps. “You have no clue.”

That’s it. I pop.

“You know, Ueli, I’m this fucking close to calling this whole thing off,” I shout. “I can’t talk to your wife. I can’t talk to your parents. And now I can’t come watch you paraglide? I’m sorry, but this is ridiculous.”

Steck answers in a low, controlled voice. Eventually, it comes out that, up there alone, Steck is just Ueli, a beginning paraglider who simply wants to learn the ropes and enjoy himself. If people find out that he’s not especially good at it, they might see him as a fool.

“You can do things that most people in the world can’t,” I say, simmering. “Are you insecure?”

The blood drains from his face. I’ve clearly crossed a line.

“There’s the person I show to the world and then there’s me, and only my wife knows me,” he stammers. “You have no clue what it’s like! People will see me mountain biking and think, ‘That’s Ueli Steck. He’s not that fast.’ They’ll see me drink a blue Rivella and think, ‘He must not want sugar.’ They’ll even judge me because of how I wear my socks.”

At last I start to get it: it’s another Swiss thing. In the U.S., we tend to be forgiving of others’ flaws, especially if they’ve parlayed them into strengths. But in Switzerland, comeback kids are rare; the Swiss find nothing at all to admire about shortcomings. You either do something well or you go practice quietly on your own until you’re competent.

In the end, the tension breaks when a bystander asks Steck for help unloading a lady from a handicap van with a busted lift. I apologize for getting flustered. Steck plays the consummate Swiss and offers me a diplomatic compromise: come climbing instead.

On the last day, I meet Steck and a British film crew at a sport-climbing area called Lehn, where knuckles of conglomerate rock punch through the pines. Nothing here is easy, and I can’t even get off the ground. With cameras rolling, Steck casts off on a route called Schweizerhalle, a 5.12c, while a friend, photographer Robert Bösch, belays him from below. He glides up the overhanging face with the strength and confidence of a climber enjoying the luxuries of a rope. Steck pauses at the crux, a bulge with thin holds that are greasy in the heat.

“Hüüü!” says Bösch, Swiss German for “You got it, bro!”

Steck dips his hands into his chalk bag, sending fine white flakes fluttering into the sunlight. He then pulls hard on the holds and guns it until he’s so high above the rest of us that there’s nowhere else to go.