The fight or flight response is your body's emergency program. When your brain reads a situation as a threat, the sympathetic nervous system releases adrenaline and cortisol, your heart beats faster, you breathe faster and your muscles tense, so you could fight or run. You can't switch it off by deciding to. But you can help your body register that the danger has passed: breathe out longer, look around, let your muscles go, and give it a few minutes.
Below: what exactly happens in the body, a 5-step plan to calm it, why a slow breath helps, how fight or flight relates to anxiety, and when it's a reason to talk to a doctor.
What is the fight or flight response?
The American Psychological Association (APA) describes it like this: the autonomic nervous system has two parts, the sympathetic and the parasympathetic nervous system. When the body is stressed, the sympathetic nervous system contributes to what is known as the "fight or flight" response, and the body shifts its energy toward fighting off a threat or fleeing from it. Once the crisis is over, the body usually returns to its unstressed state, helped by the parasympathetic nervous system, which generally has the opposite effects.
The term goes back to the American physiologist Walter Bradford Cannon (1871 to 1945). According to Encyclopaedia Britannica, he coined the terms "fight-or-flight" and "homeostasis", and his work on the emergency functions of the sympathetic nervous system appeared in Bodily Changes in Pain, Hunger, Fear and Rage (1915).
The alarm doesn't distinguish well between a bear and a deadline. APA's examples of acute stress include meeting deadlines, being stuck in traffic and slamming on the brakes to avoid an accident.
What happens in your body during fight or flight
| What changes | Source |
|---|---|
| Adrenaline (epinephrine) and cortisol are released | APA |
| The heart beats faster and contracts more strongly | APA |
| You breathe faster; the airways widen | APA, gesund.bund.de |
| Blood pressure rises; blood is directed to the large muscles and the heart | APA |
| More glucose (sugar energy) enters the bloodstream | APA |
| Muscles tense up | APA |
| Digestion, bowel and bladder activity are turned down | gesund.bund.de |
A second, slower route runs through the HPA axis (hypothalamus, pituitary gland, adrenal glands) and raises cortisol, which makes more energy available for a longer challenge (APA). NHS Every Mind Matters calls adrenaline the "fight or flight" hormone, which usually gives us a boost or motivates us to act quickly.
What you feel from the outside: a pounding heart, fast breathing, tense shoulders or jaw, a nervous stomach. gesund.bund.de names faster breathing, sweaty hands and needing the toilet more often as familiar reactions before an exam or an important appointment.
How to calm fight or flight: 5 steps
This takes about three minutes. It follows the steps of the SOS sessions in our app (name the moment, breathe out longer, orient, one small next step), plus a movement step, written out so you can do it without a phone.
- Name it. Say to yourself: "My alarm is on." The response is a normal reaction, not a sign that something is wrong with you. Naming it gives you a little distance.
- Breathe out longer than you breathe in. In through the nose for about four counts, out for about six. Five rounds. If six is too long, make it five. Don't aim for big breaths; aim for slow ones.
- Orient yourself. Lift your gaze and look around slowly. Name three things you can see, then one sound. Your eyes and ears tell your brain what's actually here right now.
- Use the energy or let it go. Your body has been prepared to move. Walk for a minute, climb a flight of stairs, or press your feet into the floor for a few seconds and release. Then let your shoulders drop and your jaw soften.
- Choose one small next step. Drink water, open a window, write down the one thing that needs doing. Then check in: you don't have to feel calm, just a little steadier than a few minutes ago.
For more quick techniques, see how to calm down fast, and for twelve ways to anchor yourself in the present, grounding techniques.
Why a slow breath helps
Relaxation techniques aim to bring about what the US National Center for Complementary and Integrative Health (NCCIH) calls the "relaxation response": slower breathing, lower blood pressure and a reduced heart rate, the opposite of the stress response.
Breathing is the one part of the alarm you can steer on purpose. A 2018 systematic review of 15 studies in healthy people found that slow breathing techniques were linked to signs of parasympathetic activity, such as higher heart rate variability, and to people reporting more comfort and relaxation. Most studies were small, so it describes a mechanism researchers find plausible, not a guarantee for every moment. Our guide to breathing exercises for stress has four exercises with a longer exhale.
What a breathing exercise can't do: make a real danger disappear. If you're in an unsafe situation, getting to safety comes first.
Fight or flight without a clear threat
Sometimes the alarm goes off when nothing dangerous is happening. NIMH describes anxiety as the body's reaction to stress that "can occur even if there is no current threat". APA notes that fast breathing caused by stress can bring on a panic attack in people who are prone to them.
The steps above can take the edge off an anxious moment. They are not a treatment for an anxiety disorder or panic attacks. If the alarm fires often, strongly or without a trigger, talk to a doctor. And if you have chest pain or breathing trouble you haven't had before, get medical help first rather than assuming it's stress.
When the alarm doesn't switch off
The fight or flight response is built for short bursts. APA describes chronic stress as the alarm being triggered over a long period, causing wear and tear on the body: "It's not so much what chronic stress does to the nervous system, but what continuous activation of the nervous system does to other bodily systems." That's why a stressful month deserves more than a breathing exercise: sleep, movement, breaks and work on the causes. What is stress explains the difference between short and long-term stress, and stress relief techniques lists what helps on each time scale.
Calm the stress response with the app
AI Meditation: Sleep & Calm has two sessions built on the steps above:
- Acute Stress SOS takes you through arriving, a 4-6 breath, a short grounding with sight, touch and sound, and one small next action.
- Understanding Stress and Overload is a knowledge session that explains the stress alarm in plain words and why it stays on when recovery is missing.
For moments of strong anxiety there's also Anxiety and Panic SOS: Steady Yourself in Minutes, a short session to steady yourself. It's a wellness exercise, not a treatment. The voices are AI voices, and you can set how long a session lasts within its range. See how the app works, try it for free, no account needed.
When to get help
The NHS suggests seeing a GP if you're struggling to cope with stress or if what you try yourself isn't helping. NIMH suggests talking to a professional if the symptoms of stress or anxiety won't go away. In an emergency, call your local emergency number.
Your health
This app is a wellness app and does not replace medical advice. If you often feel your heart racing, can't catch your breath or feel panicky without a clear reason, talk to a doctor. Chest pain or breathing trouble that is new to you needs medical help first. The NHS page on stress explains where to get help.
Sources
All pages accessed on September 25, 2026.
- American Psychological Association: Stress effects on the body (last reviewed October 21, 2024). Sympathetic and parasympathetic nervous system, hormones, HPA axis, body changes, chronic stress, hyperventilation.
- Encyclopaedia Britannica: Walter Bradford Cannon. Origin of the term, 1915 book.
- NHS Every Mind Matters: Dealing with stress. Adrenaline as the "fight or flight" hormone.
- gesund.bund.de (German Federal Ministry of Health): Stress (as of January 14, 2026, German). Alarm phase, airways, digestion turned down, familiar signs.
- National Center for Complementary and Integrative Health: Relaxation Techniques: What You Need To Know (last updated June 2021). The relaxation response.
- Zaccaro A, et al. How breath-control can change your life: a systematic review on psycho-physiological correlates of slow breathing. Frontiers in Human Neuroscience, 2018. 15 studies in healthy people, parasympathetic markers.
- National Institute of Mental Health: I'm So Stressed Out! Fact Sheet. Anxiety without a current threat, when to seek help.
- NHS: Stress (page last reviewed March 6, 2026). When to see a GP.
