Reported cases of extreme and abnormal strength, typically in life-threatening situations, are known as "hysterical strength". This usually involves someone lifting a heavy car off of someone trapped underneath, as I wrote about in thisarticle. Though no one has managed to capture video evidence of this phenomena yet, as it is rather rare, I'm sure it is only a matter of time in this age of ever-present cameras. Scientists have demonstrated how feats of hysterical strength could potentially be achieved from a biological standpoint, using hormones.
Adrenaline and noradrenaline (norepinephrine) are hormones that that trigger fight-or-flight responses in situations of high stress, and can increase heart rate and respiration, dilate pupils and slow digestion. They can also lead to more frequent muscle contractions, which may allow for superhuman feats of strength.
When the adrenal medulla, just above the kidneys, releases adrenaline, blood flows to muscles much more freely, providing them with increased oxygen supply. Lifting an object is enabled by contracting skeletal muscles, which given an increased oxygen supply, can contract at an enhanced rate. Meanwhile, adrenaline also stimulates the conversion of glycogen into glucose, providing extra energy to the muscles and increasing strength. It may actually be noradrenaline that accomplishes this, however, as this hormone is released directly at the nerve terminals and doesn't need to circulate through the veins.
But does this really translate into a small teenage girl lifting a one ton vehicle when the world deadlift record is only half of that weight? Maybe! When people are thrown several feet or more by a powerful electric shock, it is not actually the electricity that throws them, instead the muscles own reaction to the current is generating the force. So our muscles can have some pretty wild hidden capabilities.
So does that mean it's possible to perform superhuman feats of strength? The evidence is frustratingly thin here -- but there's one example of our muscles' amazing capabilities that may point to the possibility of hysterical strength, and that's what happens when our bodies are shocked with electricity. You've heard of people being thrown across rooms by shocks, or their hands clamping down on live wires so hard they can't be loosed? It's not the current that causes it, but our muscles' reaction to the current. If nothing else, it demonstrates the potential for muscle use that's not normally available to us.
