In 2006 in Tucson, Ariz., Tim Boyle watched as a Chevrolet Camaro hit 18-year-old Kyle Holtrust. The carpinned Holtrust, still alive, underneath. Boyle ran to the scene of the accident and lifted the Camaro off the teenager, while the driver of the car pulled him to safety.

In 1982, in Lawrenceville, Ga., Angela Cavallo lifted a 1964Chevrolet Impala from her son, Tony, after it fell off the jacks that had held it up while he worked underneath the car. Mrs. Cavallo lifted the car high enough and long enough for two neighbors to replace the jacks and pull Tony from beneath the car.

Marie "Bootsy" Payton was cutting her lawn in High Island, Texas, when her riding mower got away from her. Paytons young granddaughter, Evie, tried to stop the mower, but was knocked underneath the still-running machine. Payton reached the mower and easily tossed it off her granddaughter, limiting Evies injuries to four severed toes. Curious, Payton later tried to lift the mower again and found she couldnt move it.

What accounts for feats of superhuman strength like these? Are they glimpses into the lives of superheroes alter egos? Or are all of us imbued with amazing strength?

Although well-documented when they do occur, feats of hysterical strength unnatural and amazing strength tapped during high-stress situations are not recognized by medical science. This is largely due to the problem of gathering evidence: Instances like these come about without warning, and to reproduce these situations in a clinical setting would be unethical and dangerous.

But we are aware of the effects of adrenaline, a hormone shown to increase strength to amazing degrees for short periods of time. 

WOMAN VS. POLAR BEAR

Adrenaline doesnt just help people lift cars. In Ivujivik, Quebec, in 2006, Lydia Angyiou wrestled a large polar bear that she saw advancing toward her son and another boy while they played hockey. Angyiou tackled the polar bear and fought it while the boys ran for help. While Angyiou suffered some wounds, the polar bear ultimately lost the fight. Angyiou sparred with it long enough that a neighbor was able to shoot the bear four times until it died.

When we feel fear or are faced with a sudden dangerous situation, the human body undergoes an amazing change. The stressor for example, the sight of your son pinned beneath a car stimulates the hypothalamus. This region of the brain is responsible for maintaining the balance between stress and relaxation in your body. When its alerted to danger, it sends out a chemical signal to your adrenal glands, activating the sympathetic system, which sends the body into an excited state. These glands release adrenaline (epinephrine) and noradrenaline (norepinephrine), hormones that create the state of readiness that helps a human confront danger. Together, these hormones raise heart rate, increase respiration, dilate the pupils, slow down digestion and perhaps most importantly allow muscles to contract.

All of these changes in our normal physical state prepare us to face danger head-on. Combined, they make us more agile, allow us to take in more information and help us use more energy. But adrenalines effect on muscles accounts for amazing strength. Adrenaline acts on muscles, allowing them to contract more than they can when the body is in a calm or neutral state.

When adrenaline is released by the adrenal medulla an interior region of the adrenal glands, which are located just above your kidneys it allows blood to flow more easily to your muscles. This means that more oxygen is carried to your muscles by the extra blood, which allows your muscles to function at elevated levels. Skeletal muscles those attached to bones by tendons are activated by electrical impulses from the nervous system. When theyre stimulated, muscles contract, meaning they shorten and tighten. This is what happens when you lift an object, run or throw a punch. Adrenaline also facilitates the conversion of the bodys fuel source (glycogen) into its fuel (glucose). This carbohydrate gives energy to muscles, and a sudden burst of glucose also allows muscles to strengthen further.

So does this mean that we have superhuman strength that is unlocked when were confronted with danger? Thats one way to put it.

Some theorize that we normally use only a small percentage of our muscles capabilities. When we are confronted with danger, we transcend the limitations of our muscles and simply act. The rush of adrenaline, which accounts for a sudden increase in strength, helps to facilitate a person lifting a car. In other words, when confronted with extreme stress, we involuntarily use our muscles beyond the limitations of their normal voluntary use.

This theory is supported by what happens when a person is electrocuted. Someone who is shocked can be thrown a notable distance from where the shock took place. But this is not due to the electric shock. Instead, its a sudden and violent contraction of the persons muscles as a result of the electrical charge flowing through the body. This demonstrates a potential for muscle contraction that isnt utilized under normal circumstances. In much the same way that people cant throw themselves across the room, they also cant normally lift a car the resources arent available without the threat.