Have you ever found yourself in a situation where you performed physical acts you cannot ordinarily perform? I remember this one time I was going home a bit late in the night when I decided, against my best senses, to go through an alley.

On one side of the alley is a tall wall, while a chest high fence stands on the other side. Half-way through the alley, I saw two guys emerge from behind a dumpster that was a few meters in front of me. With my senses on high alert, I stopped immediately.

One of the guys started approaching me quickly. He had in his arms something that looked like a metal bar. As I started turning back the way I had come, another guy emerged from the mouth of the alley, effectively blocking my exit.

What happened next was a blur!

Without thinking, I scaled the chest high fence, run across the empty lot, scaled the fence on the other side and run all the way home. Only after I got home did I stop to think how I had escaped a possible mugging.

Pondering the escape after I was home safely, it hit me that the fence I had scaled was a bit high, and I doubt that I can ordinarily go over it as quickly and easily as I did that day. How was I able to do it?

Well, turns out I have my fight or flight response to thank for my ability to escape the muggers that day.


Civilization and modern advances in science and technology have made life relatively safe for us. Thousands of years ago, life wasn’t so easy for our ancestors. They didn’t have farms and supermarkets like we do today.

They had to roam the forests and grasslands searching for fruits, wild game and other edibles to sustain them. This presented a lot of risks. As they roamed the forests, a lion or tiger could spring from the bushes at any moment and attack them. The grasslands were filled with dangerous snakes and other reptiles.

To ensure their survival, their brains developed a mechanism that prioritized keeping them safe above everything else.

Once they sensed danger, this mechanism took over from their conscious control and prepared them to either run away from the imminent danger or to fight for their life.

This mechanism is known as the fight or flight response, and has been passed down to us over the course of evolution.

Also known as the acute stress response, the fight or flight response is a physiological reaction that occurs when your brain senses something it perceives to be a threat to your life or wellbeing. The reaction is triggered by the release of hormones that give your body a burst of energy and strength in preparation for dealing with the perceived threat.

This reaction was first described in the 1920s by Walter Bradford Cannon, an American physiologist. It was named the fight or flight response because when activated, it gives you the physical ability to either flee from the source of danger or fight the perceived threat.


When you see or hear something that your brain perceives to be a threat, your brain sounds an alarm by sending the information to the amygdala, a cluster of nuclei in the brain whose primary role is to process responses to emotion-causing stimuli.

The amygdala is particularly associated with the emotion of fear.

Once the information gets here, the amygdala processes it to decode what the information signifies.

If the information is perceived to signify danger, the amygdala immediately sends a distress signal to the hypothalamus, which is the command center for the body’s metabolic processes as well as the functions of the autonomic nervous system. This is the system that controls involuntary functions such as your heartbeat and blood pressure, breathing, and glandular processes.

The autonomic nervous system is made up of two key components: the parasympathetic and the sympathetic nervous system. These two components work in opposition to each other. You can think of them as the gas and brake pedals in a car.

The sympathetic nervous system acts as the gas pedal, initiating reactions within the body, while the parasympathetic nervous system acts as the brake pedal, slowing down the functions of the sympathetic nervous system and promoting a “rest and digest” response.

When the distress signal gets to the hypothalamus from the amygdala, the hypothalamus responds by activating two systems: the sympathetic nervous system and the adrenal-cortical system. Once the sympathetic nervous system is active, the body generally speeds up and becomes very alert, while the muscles become tense, ready for action.

Using nerve pathways to initiate reactions, the sympathetic nervous system sends out signals to the adrenal glands, triggering the release of adrenaline and noradrenaline to the bloodstream.

The release of these hormones in turn causes a number of physiological responses that prepare the body for action.

All these reactions occur instantly, before you even have a chance to consciously process the situation you are in. This explains why you are able to jump from the path of an oncoming car without actually thinking about it.

A short while after is released into your bloodstream to initiate action, the hypothalamus also releases a hormone known as CRH into your pituitary gland. This activates the adrenal-cortical system. Immediately the adrenal-cortical system is activated, the pituitary gland in turn secretes a hormone known as ACTH.

ACTH is transported through the bloodstream to the adrenal cortex, where it triggers the secretion of about 30 different stress hormones, including cortisol. The release of these hormones reinforces the effect of adrenaline and noradrenaline, continuing to provide you with energy and strength to deal with the threat.

The activation of the adrenal-cortical system can keep the sympathetic nervous system running for as long as necessary, until you are out of danger. Once the threat is neutralized, or once you have gotten away from danger, the levels of cortisol in your body decrease and the parasympathetic nervous system is activated.

It acts as the brake and counteracts the effects of fight or flight response.

Once you are away from danger, it may take anywhere between 20 – 60 minutes for your body to go back to its pre-arousal state.


The hormonal activity described above leads to a number of physiological changes as your body prepares to fight or flee from the threat. These changes include:

  • Increase in heart rate: Your heart starts beating faster as the body tries to pump blood faster to areas of the body that need fuel in order to respond to the danger.
  • Increased breathing: Your respiration rate also increases as your body tries to take in as much oxygen as it can as quickly as possible. The increase in heart rate ensures that this oxygen gets to the vital muscles quickly. The smooth muscles also relax so as to allow more oxygen to be absorbed into your lungs.
  • Dilated pupils: As your body prepares to deal with the danger, it needs to be very aware and observant of your surroundings. Therefore, your eyes become dilated in order to allow more light into the eyes and therefore improve your vision. You might also experience tunnel vision, where your peripheral vision is reduced to allow you to only concentrate on the danger ahead of you.
  • Pale or flushed skin: As your body prepares to deal with the threat, veins in your skin constrict to reduce blood flow to surface areas of the body. This blood is channeled to areas of your body that are needed at the moment, such as your brain, the arms and legs and other huge muscle blocks. The decrease of surface blood flow leads to your face looking pale. In addition, your blood’s clotting ability becomes heightened to prevent excessive blood loss in case you get injured while dealing with the threat.
  • Trembling: The fight or flight response tenses your muscles in readiness for action, like a coiled spring. This tension in the muscles can cause you to tremble.
  • Increase in blood glucose levels: The release of adrenaline triggers the release of fats and glucose (blood sugar) from temporary storage sites. The fats and glucose circulate in your blood stream and provide the extra energy needed to fight or flee from the danger.
  • Shutdown of non-essential systems: When dealing with a potential threat, your body needs all the energy available. To prevent wastage of energy, non-essential functions such as digestion and the immune system are temporarily shut down until you are out of danger. In addition, your tolerance for pain increases in order to make it possible for you to continue fighting or fleeing even in the event of injury.
  • Decreased focus on small tasks: Your brain’s entire focus is directed on the source of danger and how to deal with it, so you will have trouble focusing on small tasks and any other information that is not essential at the moment.


The fight or flight response was a very vital mechanism that ensured survival of our ancestors by allowing them to escape from tigers and bears without spending precious seconds thinking about what to do.

Even today, the fight or flight response is still important. It helps us escape from threats such as oncoming cars, growling dogs, or in my case, muggers who were after my wallet and phone. Sometimes, however, the fight or flight response can be bad for you.

You don’t have to be in physical danger in order for the fight or flight response to be triggered. Your brain only needs a perception of a threat and boom! The emergency mode gets triggered.

While the number of physically threatening situations we experience each day have reduced greatly, the fight or flight can be triggered by social situations, stresses from day to day life, and even random thoughts. The amygdala is not very good at distinguishing between situations that present physical danger to us and those that only threaten our emotional wellbeing.

Anything that causes a negative emotional response is usually treated as a threat, which explains why you may experience some of the signs of the acute stress response even in fairly non-threatening situations, such as trembling before giving a big presentation, or an increase in heart rate and respiration in response to a rude comment from your colleague.

When the fight or flight response is triggered in such situations, you are unlikely to fight or run away. The body releases a lot of energy and hormones in preparation for physical action, yet you cannot react physically to these situations.

As a result, the extra energy and the hormones are not used up, which can make it difficult for some people to get off from the acute stress response. They remain in a state of arousal.

Unfortunately, while the acute response is a powerful reaction, it is only an emergency state that is meant to be engaged for short periods of times.

Remaining in this aroused state for long periods of time can leave you exhausted and even lead to negative physical effects such as migraine headaches, high blood pressure and an increased risk of heart attack and stroke.

It can also increase the intensity of conditions such as chronic gastritis and fibromyalgia. The high levels of cortisol resulted from a prolonged acute stress response can also lead to increased appetite as the body tries to get more energy to deal with the perceived threat, thus leading to obesity and weight gain.


If you find yourself constantly or frequently experiencing the physiological symptoms associated with the fight or flight response, it is important for you to take action to tame the response before it starts having a negative impact on your health.

Fortunately, there are some techniques that you can use to calm down from the acute stress response. These include:


This is one of the best techniques for dealing with a prolonged fight or flight response. Remember, the fight or flight response is meant to prepare you for a burst of physical activity, which unfortunately does not happen in cases where the acute stress response is not triggered by physical threats.

The excess energy and stress hormones remain in your body and keep you in a constant state of arousal. When you exercise, the physical activity you engage in provides your body with a way of metabolizing the excess energy and excess stress hormones, allowing your body and mind to calm down a lot faster.

The best part about using exercise to calm your acute stress response is that anyone can do it without having to learn anything new. There are no special exercises that you need to perform. You could play soccer or tennis, run around the block, lift weights, box, and so on.

Basically, anything that can get your heart rate up and burn some calories is enough to counter the effects of the fight or flight response. Additionally, exercising also releases endorphins – the feel good hormones – into your bloodstream, thereby helping counter the stressful feeling that comes with the fight or flight response.

Remind Yourself That You Are Safe

Sometimes, the physiological changes that accompany the acute stress response can be confused for something else, leading to panic, which in turn intensifies the acute stress response, and so on.

For instance, if you are in a social situation and you heart starts racing, you might be tempted to think that you are having a heart attack. This causes you to panic.

Unfortunately, your amygdala takes the panic for a threatening situation, therefore it sends a signal to the hypothalamus which responds by triggering the release of more adrenaline and cortisol, making your heart race even faster.

To avoid this, when you find yourself experiencing some of the physical symptoms of the fight or flight response, remind yourself that you are in no actual danger, that your body is only priming for a fight and nothing more. This will prevent you from going into a loop of negative feedback that keeps reinforcing itself.

Of course, the very first times you start doing this, you won’t calm down immediately. Simply keep reminding yourself that you are under no threat, and eventually, your body and mind will calm down. As you practice this more and more, you will notice that the frequency of your acute stress responses will decrease.

Practice Relaxation Techniques

Another effective way of taming your acute stress response is to practice relaxation techniques – such as breathing exercises and progressive muscle relaxation – whenever the acute stress response strikes. Whenever you find yourself experiencing the symptoms of the fight or flight response, find a comfortable place to sit and start taking deep breaths.

Slowly inhale through your nose to a count of four, hold the breath inside your longs to a count of four, and then slowly exhale through your mouth to a count of six. When you are in the acute response mode, your breath is usually fast and shallow. Once you start taking the long, deep breaths, your body will automatically calm down and switch off the effects of the acute stress response.

The other relaxation technique is progressive muscle relaxation. To do this, start by finding a comfortable place to sit or lie down. With your eyes closed, take five deep breaths, focusing on the sensation in your lungs and diaphragm as you breathe in and out.

After the five deep breaths, focus on your right and tense all the muscles on your foot and toes as your breath in. Hold the breath for a while, and then slowly release the tension in your foot muscles as you exhale. Move to your lower leg and repeat the same exercise with your calf and shin muscles.

Tense the muscles as you breathe in, hold the breath and then slowly release the tension as you exhale. Repeat the same for your upper leg and then move on to your left leg. After you are done with the legs, move progressively to the muscles on your back, stomach, chest, shoulders, upper hand, arms, palms and fingers and finish with the muscles on your face and head.

Just like the breathing exercises, progressive muscle relaxation gets calms you down by countering one of the major effects of the fight or flight response (tension in the muscles).

Practice Mindfulness

This technique needs a lot of practice, but once you master it, it can be a very effective way for taming your acute stress response. Mindfulness involves paying attention to and being aware of the present moment in a deliberate and non-judgmental way. When you are practicing mindfulness, you take note of all the thoughts in your mind and the sensations in your body.

You separate yourself from your thoughts and sensations and simply observe them like an outsider, without any judgment. This allows you to respond in a deliberate manner, rather than being a slave to your acute stress response.

For instance, if you are about to give a huge presentation, your mind might trigger the fight or flight response, and suddenly you want to get as far away from the presentation. Instead of reacting as your brain wants, mindfulness allows you to take note of the sensation you are feeling and separate yourself from it.

Once you recognize that you are not one with the need to flee from the presentation, you can then choose how you want to proceed (making the presentation) rather than acting as your brain wants you to (getting away from the presentation).


The fight or flight response is an automatic mechanism that your brain uses to keep you safe from danger. Once the response kicks in, it gives you a burst of energy and strength and prepares your body to either flee from the threat or fight for your life.

The response is accompanied by a set of physiological changes that get your body ready for action. While the fight or flight response is a great mechanism that keeps you safe, frequent or long term activation of the acute stress response can have a negative impact on your body and health.

To prevent this, you should learn how to tame your acute stress response. This can be done through techniques such as exercising, reminding yourself that you are safe, practicing relaxation techniques and mindfulness.

How the Fight or Flight Response Works

Comments are closed.