Editor's note: The following is an excerpt from Extreme Fear: The Science of Your Mind in Danger by Jeff Wise, published on December 8 by Palgrave Macmillan (Scientific American is a Macmillan publication). Extreme Fear explores the neural underpinnings of this powerful and primitive emotion by relating instances in which people were forced to act under duress and presenting the latest findings from cognitive science. In the following passage from the chapter
entitled "Superhuman" a seemingly ordinary man performs an extraordinary feat of strength to rescue a cyclist who has been run over by a car.

Here's how it is: one minute, you're going through your daily routine, only half paying attention. And the next you're sucked into a vivid, intense world, where time seems to move slower, colors are brighter, sounds more perceptible, as though the whole universe has suddenly come into focus.
   
It was about 8:30 P.M. on a warm summer evening in Tucson. Tom Boyle, Jr., was sitting in the passenger's seat of his pickup truck, his wife Elizabeth at the wheel, waiting to pull out into traffic from the shopping mall where they'd just had dinner. The Camaro ahead of them hit the gas, spun his wheels, and jerked out onto the avenue with a squeal of rubber. "Oh my God," Elizabeth said. "Do you see that?"
   
Boyle glanced up to see a shower of red sparks flying up from beneath the chassis of the Camaro. And something else: A bike, folded up from impact. The Camaro had hit a cyclist, and the rider was pinned underneath the car. Boyle threw open the door of the truck and started running after the car.
   
For a few gruesome seconds, the Camaro plunged on, dragging along the rider, 18-year-old Kyle Holtrust, with it. One of Holtrust's legs was pinned between chassis of the car and the frame of his bike, the other jammed between the bike and the asphalt. After 20 or 30 feet, the Camaro slowed and stopped. Holtrust screamed in agony, pounding on the side of the car with his free hand.
   
Without stopping to think, Boyle reached under the frame of the car and lifted. With a sound of groaning metal, the chassis eased upward a few inches. "Mister, mister, higher, higher," Holtrust screamed.
   
Boyle braced himself, took a deep breath, and heaved. The front end lifted a few more inches. "'OK, it's off me," they boy called out, his voice tight with pain. "But I can't move. Get me out!" The driver of the car, 40-year-old John Baggett, pulled Holtrust free. At last, about 45 seconds after he'd first heaved the car upward, Boyle set it back down.
   
The biker was badly hurt, in a lot of pain, and frightened. Blood was pouring out of his wounds. Boyle knelt down and wrapped the young man in his arms, comforting him until the police and fire department arrived.

The local media celebrated Boyle's feat of compassion. The YMCA gave him an award. Newspapers and TV stations interviewed him. The fanfare flattered him and he felt extremely proud of himself. Yet to this day there's something about that evening that he can't figure out. It's no mystery to him why he did what he did—"I would be such a horrible human being to watch someone suffer like that and not even try to help," he says—but he can't quite figure out how.
   
"There's no way I could lift that car right now," he says.

Boyle, it should be pointed out, is no pantywaist. He carries 280 pounds on a six-foot-four-inch frame. But think about this: The heaviest barbell that Boyle ever dead-lifted weighed 700 pounds. The world record is 1,008 pounds. A stock Camaro weighs 3,000 pounds. Even factoring leverage, something extraordinary was going on that night.

That something was the body's fear response. When we find ourselves under intense pressure, fear unleashes reserves of energy that normally remain inaccessible. We become, in effect, superhuman.
   
Under acute stress, the body's sympathetic nervous system prepares the body for sustained, vigorous action. The adrenal gland dumps cortisol and adrenaline into the blood stream. Blood pressure surges and the heart races, delivering oxygen and energy to the muscles. It's the biological equivalent of opening the throttle of an engine.
   
Vladimir Zatsiorsky, a professor of kinesiology at Penn State who has extensively studied the biomechanics of weightlifting, draws the distinction between the force that our muscles are able to theoretically apply, which he calls "absolute strength," and the maximum force that they can generate through the conscious exertion of will, which he calls "maximal strength." An ordinary person, he has found, can only summon about 65 percent of their absolute power in a training session, while a trained weightlifter can exceed 80 percent.
   
Under conditions of competition a trained athlete can improve as much as 12 percent above that figure. Zatsiorsky calls this higher level of performance "competitive maximum strength." This parameter is not a fixed number—the more intense the competition, the higher it can go, as the brain's fear centers progressively remove any restraint against performance.
   
It's no coincidence that world records in athletic events tend to get broken at major events like the Olympics, where the stakes are highest and the pressure is the greatest. Of the eight gold medals that Michael Phelps won at the 2008 Olympics, for instance, seven were world records. Not only that, but when he crossed the finish line in the men's 100-meter butterfly in 50.58 seconds, breaking the previous Olympic record, three of the other seven swimmers who finished after him also came in ahead of the previous record.
   
But there's a limit to how fast and how strong fear can make us. We've all heard stories about panicked mothers lifting cars off their trapped babies. They've been circulating for so long that many of us assume that they must be true. Zatsiorsky's work, however, suggests that while fear can indeed motivate us to approach more closely to our absolute power level than even the fiercest competition, there's no way to exceed it. A woman who can lift 100 pounds at the gym might, according to Zatsiorsky, be able to lift 135 pounds in a frenzy of maternal fear. But she's not going to suddenly be able to lift a 3,000-pound car. Tom Boyle was an experienced weight lifter. The adrenaline of that June night gave him an edge, but it didn't turn him into the Incredible Hulk.
   
The mechanisms by which the brain is able to summon greater reserves of power have not been well explored, but it may be related to another of fear's superpowers: analgesia, or the inability to feel pain. When I'm at the gym, straining to complete the last rep of a dumbbell exercise, it's pretty hard to imagine that my muscles have the capacity to work half again harder than they already are. What I feel is screaming agony.
   
But under intense pressure—whether it's a bodybuilding competition, a kid trapped under a car, or an attacking bear—you just won't feel that pain. The body pulls out all the stops and lets you turn up the dial up to "11". You don't feel the ache of your muscles. You don't feel the pain. You just do what needs to be done.