The company’s great strength, the C.E.O. says, is that “we let you believe.” Photograph by Robbie Fimmano

The logo for Under Armour, the sporting-goods company, consists of two overlapping parabolas, opening in opposite directions, which suggest the company’s initials. If you start looking for it, you may find that you see it all the time. In 1999, Jamie Foxx wore Under Armour in “Any Given Sunday”; in 2009, in the fourth season of “Friday Night Lights,” a compassionate Under Armour sales representative helped Coach Taylor secure new uniforms for his beleaguered East Dillon Lions. The company has the exclusive rights to equip athletes at thirteen colleges, among them Notre Dame, which became an Under Armour school in January, after signing a ten-year deal that is reportedly worth around ninety million dollars. Under Armour’s roster of paid endorsers includes the skier Lindsey Vonn, the quarterback Tom Brady, and the duck dynast Willie Robertson. Its roster of unpaid endorsers includes President Obama, who was photographed clutching a pair of its high-tops on one occasion and wearing a warmup jacket on another. George Zimmerman is evidently a fan: last year, when he was detained by police after an argument with his estranged wife, he was wearing an Under Armour baseball hat. And, during an infamous “60 Minutes” interview about the attack in Benghazi, the former security contractor Dylan Davies was shown wearing a sober black T-shirt, plain except for a pair of small gray parabolas on its left breast.

These are clothes designed for serious activity, though many customers have noticed that they are no less suitable for serious inactivity. As a consequence, the logo seems to turn up anywhere in the country where people are dressed casually and comfortably, which is just about everywhere—Under Armour helps supply America’s national uniform. Even so, the company’s image is maximally sports-centric: customers are referred to as “athletes,” and the changing rooms at some stores are stocked with complimentary bottles of water, in case anyone gets dehydrated while squeezing into the tight-fitting shirts that are the brand’s signature product. The company’s athlete-in-chief is Kevin Plank, who founded Under Armour in 1996, after a college football career at the University of Maryland. “Under Armour means performance,” he likes to say, but this reputation may have been besmirched last month, in Sochi, when the U.S. speed-skating team was outraced by much of the rest of the world. Some athletes and commentators wondered whether the team’s new suits, manufactured by Under Armour in collaboration with the aerospace company Lockheed Martin, might have provided a disadvantage. Plank decried the accusation as a “witch hunt,” while carefully avoiding any criticism of the skaters themselves. He knew that there was no functional connection between the drag reduction of Under Armour’s speed-skating suits and the quality of its retail product line, but he knew that customers might confuse the two—in fact, the company had spent years and more than a million dollars on the suit in the expectation that they would.

Under Armour’s main offices occupy a former Procter & Gamble factory complex, a ten-acre cluster of warehouses on the Baltimore waterfront. The campus is bisected by an active railroad, but most of the other industrial hallmarks have been thoroughly overhauled. The concrete wharf is now a half-size football field, sodded with artificial turf, and from the window of Plank’s office you can see three molasses-storage tanks that have been refitted as cylindrical Under Armour billboards bearing portraits of three local sports heroes: Michael Phelps, Cal Ripken, Jr., and Ray Lewis. On a rainy Friday morning, Plank had just flown back from South Bend, Indiana, where he had finished negotiating the Notre Dame deal. Plank is forty-one, and he doesn’t look especially footballish: he is fit but average-sized, with a restless and analytic temperament that makes plain his allergy to indecision—he speaks, often, like a coach rushing through his halftime pep talk so he can get back to the game. Thirteen hundred people work at the Baltimore offices, all of them answering, ultimately, to the same hands-on boss; no meeting seems complete without at least a brief chorus of “Kevin wants” and “Kevin says” and “Kevin thinks.” During a recent retail-strategy session, one participant asked, only half in jest, if anyone knew Plank’s upcoming travel schedule—he wanted stores along the itinerary to be ready, in case Plank turned up for an impromptu inspection.

Plank always wears Under Armour, which doesn’t mean that he conducts business in sweatpants. He is, he says, “a Tom Ford guy,” albeit one who finds himself annoyed that twelve-hundred-dollar blazers might not be designed to withstand rough treatment. He says, “You’re telling me that nobody reinforced this button that I’m buttoning and unbuttoning twenty-five times during the course of the day? I look at that and I go, ‘How does someone accept that?’ ” On this day, he was wearing a long-sleeved black shirt, dark-gray slacks, Gucci loafers, and a Breitling watch with a face the size of a poker chip. This outfit lent a luxurious aura to the windbreaker he had on, a sleek gray prototype with a discreet black logo on the front and a less discreet neon-green vertical stripe on the back, spelling out “Under Armour” in negative space.

Plank objects when people describe Under Armour as a sportswear company, even though “sportswear” is an accurate description of just about everything it currently makes. (Under Armour can be found in all sorts of stores, but no store sells more of it than Dick’s Sporting Goods.) He sees no reason that the company’s obsession with “performance,” and with exotic materials—novel polyester blends, water-resistant cotton, extra-compressive spandex—should be limited to athletics. Plank’s favorite building on campus is the innovation lab, which requires a special key fob and a vascular scan for entry, and which retains a self-conscious air of secrecy; behind the second of two doors is a row of mannequins, all shrouded in black, like Supreme Court Justices. The lab is run by Kevin Haley, a former S.E.C. lawyer, who takes a hobbyist’s delight in the arsenal over which he presides: an assortment of 3-D printers, climate-controlled chambers, motion-capture cameras, and—for old-fashioned but crucial stress tests—washing machines. Although Haley is neither a designer nor an engineer, he can talk convincingly about the proprioceptive benefits of high-top cleats, the proper mechanics of a sports bra (it should minimize jerk, instead of trying to eliminate jostling), and the way that excessive stitching can make sneakers rigid.

In keeping with the company’s new focus, Haley downplayed Under Armour’s most specialized products even while bragging about them. “There’s nothing funner than working on a speed-skating suit,” he said. “There’s a single purpose: you want to go as fast as possible; it’s all about aerodynamics. But I think it’s even cooler to work on something you can wear to work.” One of the lab’s proudest inventions is ColdGear Infrared, an insulation system meant to provide warmth without bulk. (The technology was purportedly inspired by a “powderized ceramic” that protects military aircraft.) This fall, some of Under Armour’s winter jackets will also feature something called MagZip, a magnetic clasp system that will, Haley promises, make it easy to zip up a jacket with one hand.

Plank, too, likes to emphasize the importance of Under Armour’s non-specialized clothes, because he knows that plenty of his current and future customers really aren’t athletes, no matter how broadly one defines the term. He says, “If I told you this jacket’s been to the Himalayas, you’re going, ‘I don’t know if I’m ever going to the Himalayas, but if anything ever happens I’ve got an extra layer of protection—I’ve got something you don’t.’ It’s like a superpower.” He thinks a lot these days about making clothes you can wear with jeans. Like many ambitious C.E.O.s before him, Plank is betting that his company can broaden its focus while retaining that magical brand power which induces customers to trust, and to spend, more than they otherwise might.