Scenario Based Self Defence Training

Most of us will have heard of the body’s ‘fight or flight’ response to severe stress. The main being that it involves the release of a chemical called adrenaline. Fight or flight was a term coined by the American physiologist Walter Cannon back in the 1920s. (1)

This article digs into some of the detail around this ancient evolutionary mechanism. We also examine how understanding ‘fight and flight’ can help improve our capacity for self-defence in the 21st Century.

What’s going on in fight or flight?

While adrenaline captures all the headlines, this chemical is actually part of a double act.

When faced with a threat, the command centre of the brain, the hypothalamus sends instructions to the adrenal glands. They then increase the rate of release of the hormones noradrenaline and adrenaline into the bloodstream. (2)

Noradrenaline is a fast-moving neurotransmitter that races through the sympathetic nervous system (SNS) to start the fight or flight response. Think of it as the accelerator pedal that controls the rate of the fight or flight process. Adrenaline is slower moving but sustains the process.

Effect on the body

Adrenaline and noradrenaline target several areas of the body, latching on to cell receptors to control activity. For example they:

  • Directly bind to muscle cells throughout the body, causing them to contract harder and faster. (3,4)
  • Cause the heart to pump faster.
  • Instruct blood vessels to constrict in a way that channels blood towards the heart and muscles and away from certain organs like the stomach and skin.
  • Cause muscles below the skin contract to stimulate sweating, keeping the body cool as it prepares to act.
  • Target the lungs, widening the air passages and increasing the breathing rate so that the blood is enriched with oxygen.
  • Bind with the liver, instructing it to break glycogen down into glucose. At the same time, they lock on to the pancreas, reducing insulin production. Combined, this leads to more sugar in the blood. (4)

The Result

The increased muscular stimulation and sugar-enriched fuel and air combine. The result helps the aroused person fight harder or run faster than they would normally be capable of. In a survival situation, this can make all the difference between life and death (or serious injury).

We all recognise the symptoms of this ‘adrenaline rush’. Our heart rate increases, and we start breathing quickly, taking shallow breaths due to the muscular tension in our chests. If we were to look in the mirror, we would see the colour drain from our faces. We lose our appetite, and, in some unfortunate cases, we may empty the bladder and bowels.

What happens to the brain during fight or flight?

The body

The release of adrenaline also prepares the brain for activity, albeit in a very basic way. Blood vessels in the prefrontal cortex are constricted. This prevents us from carrying out higher-order thinking such as planning and negotiation.

However, the older limbic system is flooded with sugar-rich blood. Our survival instinct becomes highly tuned so that we can spot opportunities to escape. Our reactions, balance and coordination improve. Adrenaline also dilates the pupils to maximise light for better vision. Our other senses become hyper-sensitive too.

The mind

The arousal and adrenaline combined have proven to cause details of the situation to be stored in our long-term memory. (5) This is useful in a survival sense because it trains us to recognise and avoid dangerous situations in the future. However, this function of adrenaline also contributes to phobias and flashbacks experienced by people with post-traumatic stress disorder (PTSD).

Increased alertness and speed of response are vital when we are faced with a real threat. However, there are complications if we release adrenaline in response to imagined or abstract danger.

When we stress about jobs, relationships, COVID or life in general, our brains react as if we’re facing a genuine physical threat. The release of adrenaline into our blood then puts us in a state of hyper-arousal. We feel restless, jumpy, and irritable.

How long do the effects of elevated adrenaline last – and what happens after?

Adrenaline is always being released into the system in small quantities, so it never really runs out in healthy adults.

During ‘fight and flight’

During the ‘fight and flight’ response, we simply get an injection of it into our system.  Additionally, the effects of elevated adrenaline wane after 20 minutes to an hour. However, if you remain in ‘fight or flight’ mode, you will continue to call more adrenaline into your system.

In order to reduce adrenaline levels in the bloodstream to normal, you first have to activate the parasympathetic nervous system (PNS). This happens naturally once you have successfully neutralised a threat. Whether you have won the fight or run to safety, you will relax your muscles and start breathing more deeply. This acts as a signal for the PNS to release chemicals that slow the release of adrenaline.

What happens if the threat persists?

Fight or flight is the most talked-about reaction to a threat. However, it is only one of a series of responses that the body will make, termed the ‘defence cascade’. It runs from arousal, through fight or flight, to various states of immobility whereby the body shuts down and produces opiates. (6)

There is also a ‘freeze’ state which can best be described as fight or flight with the handbrake applied. The body is primed for action but is being held rigid. Whether we run, fight or freeze depends both on the context and our individual biology and psychology.

This leads us nicely to the next section. Here we look at how knowledge of what’s happening to our bodies during arousal can better prepare us for self-defence.

The power of knowledge

When faced with a real threat to life or limb, is it better to run, fight or do both?

Some people naturally gravitate towards either fighting or running but the best course of action will depend on the context.

When flight is better

In most cases, running away is the smart choice. Few conflicts are worth sacrificing our lives for and we never really know how well equipped an opponent might be. For example, they could be armed with a weapon or have support from multiple allies. In addition, they are just as likely to be pumped up with adrenaline as you. Unfortunately, some opponents under the influence of alcohol or drugs, maybe even more capable of winning a physical fight than someone high on adrenaline.

Meanwhile, if you are backed into a corner against a determined attacker, fighting might be your only option.

Understanding panic

Some people’s response to an adrenaline rush is to panic. Again, understanding the biochemistry of fight or flight helps to explain this. With blood diverted away from the planning centre of the brain, we struggle to think clearly becoming confused and disorientated.

However, we can learn to use those vital seconds to access our enhanced sensory awareness. Combined with trusting our muscles to react correctly, we can use our brain and body together. Even if we are trapped in a corner, we can assess our opponent’s weak points. For example, identifying the most sensible escape route and acting efficiently to fight our way to freedom.

Effective self-defence training empowers us with simple to use techniques that we can deploy without thought.

Dealing with imagined threats

Knowledge of how the body reacts to threats can help us stay healthy day-to-day and even live longer. It all leads to understanding the function of adrenaline. We can see why elevated levels of it in our blood are linked with multiple health issues.  Such examples include high blood pressure (which increases the risk of heart attack and stroke), anxiety, insomnia, and obesity.

Relaxation and deep breathing help the PNS slow down adrenaline production. With this knowledge, we can take control of the process ourselves. Deep breathing, exercises, and activities such as yoga can trigger the so-called ‘rest and digest’ mechanism. Ultimately, this mechanism brings our bodies back into balance. (4).


As with all animals, our bodies have evolved over millennia. Without an effective ‘fight or flight’ mechanism, we would never have survived as a species to get this far.

However, fight or flight is a primitive mode of activity that is designed for extreme threats. It was not designed with the complexities of modern life in mind. Since those early days, humans have developed a more advanced forebrain than other animals. These developments help us build complex social networks and plan for the future. Yet when we feel threatened, even in an abstract way, the old system of defence still does its job of priming the body for emergency action.

Unfortunately, we have become distanced from our natural instincts. This has hampered our natural ability to defend ourselves when we need to. We have the tools to look after ourselves, but we have forgotten how to use them.

By understanding the way our bodies work on a biochemical level, we can take the best of both worlds. We can harness our primal instincts to fight and run when needed. At the same time, we can learn strategies to handle both real and imagined threats in the most effective way.


  1. https://www.verywellmind.com/what-is-the-fight-or-flight-response-2795194
  2. https://www.yourhormones.info/hormones/adrenaline/
  3. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1348716/
  4. https://www.healthline.com/health/adrenaline-rush
  5. https://www.ncbi.nlm.nih.gov/books/NBK3907/
  6. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4495877/