This is what the human body can do when pushed to the limit:

“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.”

via scientificamerican.com

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.