How slow breathing affects the nervous system
Breathing usually happens automatically. The brain adjusts breathing rate and depth according to the body’s needs without requiring conscious attention. At the same time, we can deliberately hold our breath, take a deeper breath or slow the rhythm. This combination makes breathing a distinctive link between voluntary actions and the body’s automatic regulatory systems.
⠀
When breathing becomes slower and more controlled, it affects the interaction between the lungs, heart, blood pressure and nervous system. Heart rate may begin to follow the breathing rhythm more clearly, while signals through the parasympathetic nervous system may have a stronger influence on cardiac regulation.
⠀
Many people therefore experience less bodily tension, a calmer pulse and improved concentration during slow breathing. However, the effect is not caused by a single nerve being “switched on”. Several mechanisms operate simultaneously, and the response varies between individuals.
⠀
What counts as slow breathing?
An adult at rest often breathes approximately 12–20 times per minute, although a normal breathing rate varies according to age, body position, emotional state, physical fitness and health.
⠀
In research, slow breathing usually refers to a deliberate breathing rate below ten breaths per minute. Many breathing exercises use approximately five to six breaths per minute, but this is not necessarily the best rhythm for everyone.
⠀
Slow breathing is not only about the number of breaths. Breathing should remain calm and comfortable without each breath becoming unnecessarily large. A person who inhales and exhales very large volumes of air may ventilate more than the body requires, even when the breathing rate is low.
⠀
Comfortable slow breathing is often characterised by:
A calm flow of air
Relaxed shoulders
Little unnecessary movement in the upper chest
A smooth transition between inhalation and exhalation
A breathing depth that feels comfortable
No pronounced dizziness or feeling of breathlessness
⠀
Breathing is controlled both automatically and consciously
The basic breathing rhythm is generated in the brainstem. Networks of nerve cells send rhythmic signals to the diaphragm and other respiratory muscles.
⠀
Breathing regulation is influenced by the levels of carbon dioxide, oxygen and acidity in the blood. Carbon dioxide has a particularly important role. When its concentration rises, the respiratory centre will normally increase ventilation so that more carbon dioxide is exhaled.
⠀
Areas of the cerebral cortex can also temporarily override the automatic rhythm. This allows us to speak, sing, hold our breath and perform deliberate breathing exercises.
⠀
When you reduce your breathing rate, the nervous system must coordinate several processes:
Activity in the diaphragm
The duration of inhalation and exhalation
The volume of air in each breath
Gas exchange in the lungs
Signals from the chest and airways
The interaction between breathing, heart rate and blood pressure
⠀
Slow breathing is therefore more than a simple movement of air. It is a rhythmic activity that affects several signalling pathways between the body and the brain.
⠀
The autonomic nervous system regulates bodily alertness
The autonomic nervous system controls functions that mainly occur without conscious control. These include heart rate, blood pressure, digestion, sweating, pupil size and regulation of the blood vessels.
⠀
The system is often divided into a sympathetic and a parasympathetic branch. The sympathetic branch helps mobilise the body during activity, danger and demanding situations. The parasympathetic branch supports functions such as digestion, energy storage and regulation of the heart during rest.
⠀
This division can create the impression that the two systems work like a simple on-and-off switch. In reality, regulation is more complex. Both branches can be active at the same time, and their activity may differ between organs.
System | Typical function | Possible effect of slow breathing |
Sympathetic nervous system | Mobilises the body during activity and strain | Bodily arousal may decrease in some people |
Parasympathetic nervous system | Supports resting functions and regulates the heart | Vagal influence on the heart may become more apparent |
Sensory nerve signals | Carry information from the lungs and chest | The breathing rhythm provides regular signals to the brain |
Brain control systems | Regulate attention and interpretation of bodily signals | Focusing on breathing may reduce attention to competing stimuli |
⠀
Slow breathing particularly affects parasympathetic regulation of the heart. This regulation is largely mediated through the vagus nerve, although the vagus nerve is only one part of a broader interaction between the brain, heart, lungs and blood vessels.
⠀
Heart rate follows the breathing rhythm
Heart rate is not completely regular, even when the body is resting. The interval between heartbeats varies continuously, and part of this variation follows breathing.
⠀
In many people, heart rate rises slightly during inhalation and falls during exhalation. This is known as respiratory sinus arrhythmia. Despite its name, it is usually a normal physiological variation rather than a disease-related heart rhythm disorder.
⠀
During inhalation, parasympathetic braking of the heart temporarily decreases. Heart rate may therefore rise slightly. During exhalation, vagal influence becomes stronger again, and heart rate often falls.
⠀
When breathing is rapid, these changes occur over short periods. When breathing slows, heart rate has more time to rise and fall during each breathing cycle. The difference between heart rate during inhalation and exhalation may therefore become more pronounced.
⠀
This does not necessarily mean that average heart rate falls dramatically. The most noticeable change may instead be that the heart rhythm becomes more wave-like and more closely coordinated with breathing.
⠀
Heart rate variability may increase
Heart rate variability, commonly abbreviated as HRV, describes variation in the time interval between consecutive heartbeats. An average heart rate of 60 beats per minute therefore does not mean that exactly one second always passes between each beat.
⠀
HRV is influenced by several factors:
Breathing rate
Breathing depth
Body position
Age
Physical fitness
Sleep and recovery
Psychological and physical strain
Alcohol and certain medicines
The time at which the measurement is taken
⠀
During slow breathing, the component of HRV that is closely associated with parasympathetic regulation of the heart often increases. This occurs partly because the difference between inhalation and exhalation becomes greater.
⠀
This does not mean that a high HRV value during a breathing exercise automatically indicates better health. The breathing pattern directly affects the measurement itself. An HRV measurement taken during controlled breathing cannot therefore be directly compared with one taken during normal spontaneous breathing.
⠀
HRV must always be interpreted in context. A single value provides limited information unless the breathing rate, measurement method, body position and surrounding conditions are known.
⠀
The baroreflex connects blood pressure and heart rate
Blood pressure changes slightly from moment to moment. To limit large fluctuations, the body has pressure-sensitive receptors in areas including the carotid arteries and the aorta. These receptors form part of the baroreflex.
⠀
When the receptors detect an increase in blood pressure, signals are sent to the brainstem. The nervous system can then reduce heart rate and adjust activity in the blood vessels. When blood pressure falls, the response may move in the opposite direction.
⠀
Breathing affects pressure within the chest and the amount of blood returning to the heart. Rhythmic changes therefore occur in both blood pressure and heart rate.
⠀
During slow breathing, these fluctuations may become more closely coordinated with the baroreflex. In many people, the interaction becomes particularly noticeable at approximately five to six breaths per minute. Breathing, heart rate and blood pressure may then begin to fluctuate at approximately the same rhythm.
⠀
This rhythm is sometimes described as the body’s resonance frequency. This does not mean that six breaths per minute is universally correct. The most effective frequency differs between individuals and may be either higher or lower.
⠀
The vagus nerve is important but does not explain everything
The vagus nerve is a central part of the parasympathetic nervous system. It carries signals between the brainstem and several organs in the chest and abdomen.
⠀
Some nerve fibres send signals from the brain to the heart and help slow the heart rate. Other fibres carry information from the organs back to the brain. The vagus nerve is therefore not simply a pathway that sends “calmness” from the brain to the body.
⠀
Slow breathing can affect vagal regulation of the heart through the changes that occur between inhalation and exhalation. Several other systems are also influenced:
The baroreflex
Pressure conditions within the chest
Sensory signals from the lungs
Attention to bodily sensations
The brain’s interpretation of safety and strain
Rhythmic activity in the cardiovascular system
⠀
It is therefore too simplistic to say that slow breathing merely “stimulates the vagus nerve”. A more precise explanation is that breathing affects an entire network of regulatory mechanisms in which the vagus nerve has an important role.
⠀
The brain receives regular signals from breathing
The brain continuously receives information from the lungs, airways, respiratory muscles and chest. This information indicates how deeply and rapidly we are breathing and how much resistance the respiratory muscles encounter.
⠀
When breathing becomes slow and regular, many of these signals also become more rhythmic and predictable. This may make it easier to direct attention towards one stable bodily process.
⠀
This focus can itself influence the experience of tension or unease. When attention shifts towards a calm breathing rhythm, competing thoughts and external stimuli may receive less attention. This does not mean that every worry or stress response disappears, but bodily activation may feel more manageable.
⠀
Breathing may also influence activity in areas of the brain involved in emotional regulation, attention and awareness of bodily signals. The exact significance of these changes is not fully understood, and studies use different breathing methods and measurement techniques.
⠀
A longer exhalation may feel calming
Many breathing exercises use an exhalation that lasts slightly longer than the inhalation. One reason is that heart rate often falls during exhalation as vagal influence on the heart increases.
⠀
A longer exhalation may therefore make the heart-slowing phase of the breathing cycle more prominent. Some people experience this as calming.
⠀
However, the evidence does not show that exhalation must always be considerably longer than inhalation. Even breathing with approximately equal inhalation and exhalation times can influence HRV and the interaction between the heart and breathing.
⠀
The rhythm should normally feel comfortable. When a very long exhalation produces breathlessness, tension or an urge to take a large compensatory breath, the breathing pattern is probably too demanding.
⠀
Calm breathing is not the same as taking very large breaths
The instruction to “breathe deeply” can cause people to inhale as much air as possible. This may become uncomfortable when each breath is much larger than the body requires.
⠀
When ventilation becomes excessive, more carbon dioxide is exhaled than the body is producing. The carbon dioxide concentration in the blood may then fall. This can affect the blood vessels in the brain and increase the sensitivity of the nervous system.
⠀
Signs that you may be breathing too much include:
Dizziness
Tingling around the mouth
Tingling in the fingers
Pressure or a light sensation in the head
Feelings of unreality
Tightness in the chest
A growing urge to take large breaths
⠀
These reactions do not usually mean that the body is receiving too little oxygen. They may instead occur because ventilation is too high in relation to the amount of carbon dioxide being produced.
⠀
When these symptoms occur, you should stop forcing the breath and return to a natural rhythm. The aim is slower and calmer breathing, not the largest possible volume of air.
⠀
How to practise slow breathing
A simple breathing exercise does not need to be complicated. It is usually better to begin with a moderate reduction in breathing rate rather than immediately attempting to reach a specific rhythm.
⠀
One possible approach is:
Sit or lie in a comfortable position
Allow the shoulders and jaw to relax
Breathe gently through the nose when this feels natural
Let the inhalation last approximately four seconds
Exhale gently for approximately five or six seconds
Avoid filling the lungs completely
Continue for two to five minutes the first time
Return to normal breathing if you become dizzy or uncomfortable
⠀
This rhythm produces approximately six to seven breaths per minute. Some people may prefer a slightly faster rhythm, such as three seconds in and four seconds out. Others are more comfortable with inhalation and exhalation of equal length.
⠀
Breathing pattern | Approximate rate | When it may be suitable |
3 seconds in and 3 seconds out | 10 breaths per minute | A gentle starting point |
4 seconds in and 4 seconds out | 7.5 breaths per minute | Even and symmetrical breathing |
4 seconds in and 6 seconds out | 6 breaths per minute | When a longer exhalation feels comfortable |
5 seconds in and 5 seconds out | 6 breaths per minute | A common rhythm in HRV biofeedback |
⠀
These figures are examples rather than requirements. The best rhythm is one that can be maintained without strain, dizziness or a strong feeling of breathlessness.
⠀
The effect varies between individuals
Slow breathing does not feel the same for everyone. Some people notice a clear reduction in bodily activation after a few minutes, while others experience little difference.
⠀
The response may be influenced by:
The person’s usual breathing rate
How deeply the person breathes
Body position
Age and physical fitness
Stress levels before the exercise
Previous experience with breathing exercises
Heart and lung function
Medicines that affect heart rate or blood pressure
The amount of attention directed towards bodily sensations
⠀
People who are highly focused on breathing, heart rate or other bodily sensations may sometimes become more anxious when trying to control their breathing. A less structured approach, such as gentle walking or focusing attention on the surroundings, may be more suitable in these cases.
⠀
Slow breathing is therefore a possible regulatory tool, but it is not a universal solution that affects everyone in the same way.
⠀
When can slow breathing be useful?
Slow breathing can be used as a short-term strategy in situations where the body is activated but there is no immediate physical danger. It may also be practised regularly to improve awareness of bodily responses.
⠀
Situations in which it may be useful include:
Before a difficult conversation
Before a presentation or examination
After a stressful period at work
As part of a calm evening routine
Between demanding work tasks
During relaxation after physical activity
As part of HRV biofeedback or other guided treatment
⠀
Breathing exercises should not be used to push through serious or unexplained symptoms. They also do not replace treatment for diseases affecting the heart, lungs or nervous system.
⠀
Common misconceptions
Slow breathing does not switch off the stress system. The sympathetic nervous system does not disappear. Breathing can influence the balance and interaction between several regulatory mechanisms, but the body retains its ability to mobilise when necessary.
⠀
More air does not necessarily produce more calm. Very large breaths can cause overventilation and lead to dizziness, tingling and increased unease. Calm breathing should be comfortable rather than maximal.
⠀
Six breaths per minute is not correct for everyone. Many people develop clear physiological fluctuations around this frequency, but individual resonance frequency varies.
⠀
High HRV during a breathing exercise is not a direct measure of health. Breathing rate affects the HRV measurement. The result must be interpreted according to how and when it was recorded.
⠀
A long exhalation is not always better. A slightly longer exhalation may suit many people, but it should not be so long that it causes tension or breathlessness.
⠀
Slow breathing does not treat every form of stress or anxiety. Breathing may reduce certain bodily symptoms, but persistent or severe difficulties may require broader assessment and treatment.
⠀
When should symptoms be assessed?
It is normal to notice changes in heart rate, breathing and bodily tension during a breathing exercise. Mild and temporary dizziness may occur when breathing is too deep, but repeated or severe symptoms should not be ignored.
⠀
The breathing exercise should be stopped if it causes:
Pronounced breathing difficulty
Chest pain
Fainting or severe dizziness
New or marked palpitations
Bluish lips or fingers
Sudden weakness or paralysis
Persistent confusion
Symptoms that continue after normal breathing has resumed
⠀
Acute chest pain, severe breathing difficulty, fainting or sudden neurological symptoms should be assessed promptly by a healthcare professional.
⠀
People with serious heart or lung disease should be cautious with prolonged breathing exercises and may benefit from professional guidance if the exercises cause symptoms.
⠀
Summary
Slow breathing affects the nervous system through interactions between the respiratory muscles, heart, blood pressure, baroreflex, vagus nerve and the brain’s processing of bodily signals. When breathing rate decreases, heart rate may follow the breathing rhythm more clearly, while vagal regulation of the heart may become more prominent. This can increase heart rate variability during the exercise and may contribute to a feeling of reduced bodily tension. Breathing should be calm and comfortable rather than maximal. Six breaths per minute may suit many people, but there is no universal rhythm. Slow breathing is generally a safe regulatory tool, but it should not be used to ignore serious or persistent symptoms.
⠀
Sources
Zaccaro A, Piarulli A, Laurino M, Garbella E, Menicucci D, Neri B, Gemignani A. How breath-control can change your life: A systematic review on psycho-physiological correlates of slow breathing. Frontiers in Human Neuroscience. 2018;12:353.
Russo MA, Santarelli DM, O’Rourke D. The physiological effects of slow breathing in the healthy human. Breathe. 2017;13(4):298–309.
Laborde S, Allen MS, Borges U, et al. Effects of voluntary slow breathing on heart rate and heart rate variability: A systematic review and a meta-analysis. Neuroscience & Biobehavioral Reviews. 2022;138:104711.
⠀
⠀
