A 16-year-old boy lifts a Volkswagen off his pinned neighbor. A mother fights off a polar bear to protect her children. A daughter heaves an overturned tractor from atop her father. These feats are made possible by a rush of adrenaline and by unlocking bodily systems and muscle capacity that are only fully accessed in moments of extreme duress.
While these incidents of so-called “hysterical strength” are real, the phenomenon is tricky to study in the lab because doing so would be dangerous to participants. Instead, neuroscientists build on what’s known about the brain and body’s fight-or-flight response and the stress feedback mechanisms associated with it that fuel these acts of extreme strength.
These are the same response systems that served our ancient ancestors in situations like confronting or fleeing from a saber tooth tiger, but they have evolved so that less extreme mechanisms are triggered in modern-day situations like when we get a troubling text message from a loved one, slam our brakes when an animal darts across the road, or are faced with the prospect of public speaking.
In each case, “it’s the same stress response, but is now more frequently activated in non-life-threatening situations,” says Marc Dingman, an associate professor of biobehavioral health at The Pennsylvania State University.
These mechanisms exist as part of the body’s autonomic nervous system, which can be thought of as a continuum, suggests popular Stanford Medicine researcher and neuroscientist, Andrew Huberman. “On one end of this continuum, you have absolute panic and the physiological responses related to that,” he explains, “and on the opposite side you have coma.”
Between these two extremes exist a range of biological responses to stress, some of which are relatable like when you lose your appetite or have trouble sleeping. Other responses are known to far less people, such as those who have experienced a moment of hysterical strength.
Understanding hysterical strength and the fight-or-flight response
Hysterical strength is a term sometimes used to describe “feats of strength occurring in high-stress situations that greatly exceed what we would normally imagine a person being able to produce and which would be impossible to reproduce in calmer circumstances,” says E. Paul Zehr, a professor of sensorimotor neuroscience at the University of Victoria in Canada.
People may experience this phenomenon when they are in extreme danger—such as falling through a frozen lake, getting attacked by a human or an animal, being trapped by an object, or when facing a natural or manmade disaster.
“The same response can also occur when intervening to protect another person in danger, so it’s not only for self-protection,” says Massimo Testa, a sports medicine physician at Intermountain Medical Group in Utah.
In such circumstances, research shows that complex brain structures, neurotransmitters, and specific bodily systems kick in to release a cascade of hormones, allowing greater access to muscle capacity and increased blood flow to the appendages and organs of the body most needed to respond to the emergency.
To further help the body accomplish this state of hyper-arousal, energy that is normally utilized in other systems around the body—such as those related to seeking and digesting food, managing reproductive health, or regulating body temperature—are diverted to focus on immediate survival.
“Any organism—human or otherwise—essentially has only three basic responses to any kind of stressor: stay put, move forward, or back away,” says Huberman. While bodily resources are needed for any of these responses, it’s the fight and flight options that require the most mobilization of resources, focusing all attention on the same objective.
“In this state, the frame rate on your perception of time drastically increases and you start micro-slicing time, taking in much more information than you normally would—and much quicker,” explains Huberman.
During such extreme stress you may also use more of your muscles than you would ordinarily be able to access. “We’re generally utilizing only a fraction of our muscles’ maximal strength and power and there’s usually plenty in reserve that remains untapped,” says Gordon Lynch, director of the Centre for Muscle Research at the University of Melbourne in Australia.
Research shows there are multiple inherent safeguards that specifically prevent muscles from being overloaded. During an emergency, however, Lynch explains that these safeguards can “be overridden to enable the instantaneous recruitment of the largest and fastest muscle fibers needed for explosive force and power and for the muscle’s true potential to be realized.”
The part hormones play
Fight-or-flight responses like these originate in the amygdala—a complex brain structure, “which processes your experiences for their emotional content,” says Donald Katz, a psychologist and behavioral neuroscientist at Brandeis University in Massachusetts. He explains that when this structure is confronted by a stressor, it sends a distress signal to an area of the brain called the hypothalamus.
The hypothalamus is like a command center for the autonomic nervous system—a system that has two divisions known as the sympathetic nervous system and the parasympathetic nervous system.
These systems control multiple involuntary bodily functions including cardiovascular and respiratory performance and the constriction and dilation of key blood vessels and small airways in the lungs.
When a stress response is activated in the hypothalamus, neurotransmitters are released from neurons throughout the body and a signal is sent to the adrenal glands, which are located on top of both kidneys.
From there, a rapid release of the hormones adrenaline (epinephrine) and noradrenaline (norepinephrine) occurs.
This hormone release, “increases heart rate and blood pressure, expands the air passages to maximize oxygen, and triggers the blood vessels to contract, which helps to re-direct blood toward major muscle groups including the heart and lungs,” says Holly Blake, a professor of behavioral medicine at the University of Nottingham Medical School in England.
Senses related to touch, sight, and sound are also heightened by the release of these and other hormones, which all serve to help you better process and respond to any sudden changes in your environment.
Of particular importance, adrenaline can also transiently reduce the sensation of pain. “Adrenaline can affect pain perception by inhibiting signaling pathways,” explains Mihail Zilbermint, a physician and the director of the endocrine hospitalist program at Johns Hopkins Medicine. It does this, in part, by intercepting and blocking pain signals traveling through the brain and spinal cord. A flood of endorphins is also often involved, which research shows act as natural painkillers.
It’s because of these hormones that one can strain or overload a muscle during moments of tremendous stress. “Your pain feedback pathways ordinarily work to protect you, but when these pathways shut down, you’re no longer concerned with tearing a bicep or dislocating a shoulder as you’re instead trying to defend yourself or a loved one against catastrophic harm,” explains Huberman.
Stress responses affect all
While extreme fight-or-flight stress responses can be beneficial and even essential for survival in emergencies, a smaller quantity of these hormones are released under more ordinary circumstances.
“Everything that happens within this response system exists on a continuum, so someone that’s a little bit stressed will experience some of this while someone in full panic mode will unlock the full effects of this system,” says Huberman.
Indeed, research shows that stress hormones such as cortisol, adrenaline, and noradrenaline are released often in most of us. “Adrenaline is produced whenever there is stress,” explains Melissa Leber, a physician and the director of Emergency Department Sports Medicine at the Mount Sinai Health System in New York City. “It can be during a competition or performance, because of an important test or presentation, when in a fight, or when your body is dealing with illness or an infection.”
And because some people are already experiencing stress more often than others, those individuals tend to experience stress responses more frequently and often to greater degrees.
Someone at a demanding job or someone who is regularly not getting enough sleep, for instance, is more likely to be “tired and wired for stress,” as Huberman puts it, than someone who doesn’t struggle with those things.
Conversely, and further up the continuum, “extreme endurance or power athletes almost certainly activate more of this stress system and for longer periods of time than is usual for the rest of us,” Zehr says.
In either case, an individual will likely experience short-term benefits associated with the release of stress-related hormones, but the long-term consequences of these hormones frequently flooding one’s system can be worrisome. “We need these hormones to facilitate physiological responses, but in excess, they can be our undoing,” Lynch says.
The consequences of experiencing extreme stress
Lynch explains that the chronic stress that’s associated with sustained, higher releases of adrenaline, noradrenaline, and cortisol, “can take their toll on the body’s organs and systems, leading to detrimental physiological outcomes.” Common adverse effects of chronic stress include high blood pressure, sleep disorders, diabetes, obesity, and heart disease.
Stress can also affect the part of the brain where memories are stored. “While stress impacts your memory dramatically in the short term and particularly in fight-or-flight situations—likely because your brain wants to remember how to avoid a similar situation in the future—in the long-term, chronic stress can significantly impair your memory,” explains Huberman.
And the extreme end of this stress response, such as what’s associated with hysterical strength and fighting or fleeing, can lead to especially worrisome outcomes.
“The physiological cascades that lead to the expression of ‘hysterical strength’ by their very nature remove safety limits and can thereby be extraordinarily dangerous,” says Zehr. “If we were at maximum all the time, we would not live very long.”
Blake says that even the incidental release of too much adrenaline such as what happens when the body anticipates a threat that never manifests, “can cause symptoms such as dizziness, insomnia, a jittery nervous feeling, and, in more serious cases, damage to the heart.”
In cases where trauma is also associated with the extreme end of a stress response, a person could suffer from post-traumatic stress disorder (PTSD) and be affected for long periods of time.
Even without a PTSD diagnosis, experiencing a high-stress response can be hard for many people to come down from emotionally. Huberman explains that fight-or-flight mechanisms necessarily activate very quickly, “but deactivating these responses tends to take much longer and some people will still be ruminating on the experience hours or days later.”
Such people may have difficulty concentrating, their appetite may be affected, and they may struggle with sleep at night.
“We’re human,” says Huberman, “and sometimes when we are stressed, we can’t just turn it off.”
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