Most people assume breathing is automatic and “good enough", however lots of us don’t habitually use the lower diaphragm and belly for slow, easy breaths. Instead we default to shallow, rapid chest-breathing (sometimes called upper-chest or clavicular breathing) or patterns that meet the moment (stress, posture, screen time) rather than the body’s long-term needs. Clinically this shows up as “dysfunctional breathing”—a recognizable pattern of irregular, often shallow or over-rapid breaths that happens even when there’s no primary lung disease. Estimates put dysfunctional breathing at roughly ~9% in the general adult population and it’s much higher among patients seen for breathing complaints or asthma. 

Below I explain, with research-backed references, why diaphragmatic (lower-belly) breathing helps, what happens physiologically when we don’t breathe well and simple, evidence-based ways to practice better breathing.

What “good” breathing looks like

• The diaphragm (a large dome muscle beneath the lungs) should do most of the work at rest: on inhalation it drops and the belly gently rises; on exhalation it relaxes and the belly falls.
• A typical healthy adult resting respiratory rate is about 12–20 breaths per minute (many clinical sources use 12–16 or 12–20 as the normal range). Slow, deep diaphragmatic breathing practiced intentionally is often much slower (see below). 

How many people are “chest breathers”?

There isn’t one widely-agreed single statistic for “percent who breathe from the chest” — researchers typically measure dysfunctional breathing instead (which often includes thoracic/chest-dominant patterns). Dysfunctional breathing affects roughly one in ten people in community samples and is more common in clinical populations and people with asthma (where studies have found rates around 25–30% in some primary-care samples). So while “chest-breather” as a lay label is imperfect, a nontrivial minority of people have breathing patterns that are suboptimal and clinically meaningful. 

Why Learning to Breathe well is A Practice

Good breathing is a motor habit tied to posture, stress reactivity and awareness. Research shows that deliberate training — slow diaphragmatic or “resonance-frequency” breathing and breathing retraining programmes — reliably changes physiology (heart-rate variability, blood pressure, stress hormones) and symptoms over weeks to months. That means breathing well doesn’t always “click” once; it takes regular practice, cueing, and sometimes professional coaching. 

The Physiology — Why the Lower Diaphragm Matters

1. Vagal tone & the parasympathetic system

Slow, diaphragmatic breathing increases cardiac vagal activity (measured as heart-rate variability or HRV) — a marker of parasympathetic (rest-and-digest) activation. Higher vagal tone improves the body’s ability to down-regulate stress responses and supports emotional and physiological resilience. Randomized and controlled studies show meditative or diaphragmatic breathing increases vagal markers compared with control conditions. 

2. Blood pressure and autonomic balance

Breathing at or near an individual’s “resonance frequency” (often around ~5–7 breaths per minute) amplifies baroreflex function and can lower resting blood pressure and heart rate over time. Clinical trials of resonance-frequency or slow-breathing training show improvements in blood-pressure control and autonomic balance. 

3. Stress hormones (cortisol) and stress symptoms

Several trials and controlled studies report that adding slow, deep breathing or breathing + mindfulness reduces cortisol and perceived stress versus control activities. Because cortisol is a major mediator of the chronic stress response, breathing practices that reduce cortisol are a direct pathway for lowering physiological stress–related symptoms (including tension and clenching). 

4. Muscle tension, Jaw Clenching and Pain

Chronic stress and elevated sympathetic drive are linked to increased jaw/clenching behaviors (bruxism) and to musculoskeletal tension in the neck and upper back. Systematic reviews and clinical studies show associations between stress markers (including cortisol) and bruxism/TMD symptoms. By reducing sympathetic arousal, better breathing practice can reduce nocturnal and daytime muscle tension, which helps with jaw tension and related neck/upper-back pain. 

What Goes Wrong When We Breathe Poorly (hyperventilation, shallow breathing, chest dominance)

• Hyperventilation (too rapid / too deep relative to metabolic need) lowers carbon dioxide (CO₂) in the blood (hypocapnia). Hypocapnia causes cerebral vasoconstriction — less cerebral blood flow — which paradoxically can reduce oxygen delivery to the brain even though you’re “breathing more.” This state also raises sympathetic activity. The net result: anxiety, lightheadedness, brain fog, and in vulnerable people, worsening fatigue and cognitive overload. 
• Sustained sympathetic activation from poor breathing increases allostatic load (wear and tear), contributing to burnout when combined with psychosocial stressors. 
• Breathing and airway problems: behavioural or voluntary hyperventilation can precipitate bronchoconstriction in asthma and is commonly seen as a comorbidity in people with asthma and unexplained dyspnea; dysfunctional breathing patterns also complicate asthma control. There is also clinical literature describing behavioural hyperventilation’s links with sleep-disordered breathing in specific cases. 

How Many Breaths per Minute Should We Take?

• Normal resting adults: ~12–20 breaths per minute per clinical sources. 
• For training and vagal benefits: research on resonance-frequency breathing and HRV often targets ~4.5–7 breaths per minute (commonly around 6 breaths/minute) for short practice sessions; this slower rate is used intentionally in breathing training to stimulate vagal tone and baroreflex function. It is not the usual spontaneous resting rate for most people, but a therapeutic practice rate. 

Practical, Evidence-Based Breathing Practices (how to start)

1. Gentle diaphragmatic breathing (beginner; 5–10 minutes)

• Sit or lie comfortably with one hand on your chest and one on your belly.
• Inhale slowly through the nose for ~4 seconds, feel the belly rise (chest should move very little).
• Exhale slowly for ~6 seconds through the nose or pursed lips.
• Repeat for 5–10 minutes once or twice daily. Over weeks you’ll notice calmer baseline arousal. (This pattern is a simple, safe way to start training diaphragmatic breathing; studies of slow breathing protocols show physiological benefits after repeated practice.) 

1. Resonance-frequency practice (if you want measurable HRV/BP effects)

• Many labs use guided paced breathing at ~6 breaths/min (inhale about 5–6 seconds, exhale about 5–6 seconds) for 10–20 minutes. This is often done with a coach, app, or biofeedback to find your personal resonance. Clinical trials using resonance-frequency training report improvements in HRV and blood pressure. 

1. If you feel dizzy or lightheaded: slow down, breathe shallower, and re-introduce nasal breathing and longer exhales. If symptoms persist, stop and consult a clinician. (Hypocapnia from too-fast or overly deep breathing can cause dizziness and other symptoms.) 
2. For chronic or complicated symptoms (asthma, chronic dyspnea, suspected dysfunctional breathing): consider referral to a respiratory physiotherapist, a clinician trained in breathing retraining (e.g., Buteyko or Papworth methods studied in respiratory clinics), or multidisciplinary care; breathing retraining has evidence of benefit for people with dysfunctional breathing and for some patients with poorly controlled asthma. 

A balanced View & Safety Notes

• Breathing practice is widely beneficial and low-risk for most people, but some conditions (severe COPD, unstable cardiac conditions, certain psychiatric states) need medical oversight; always check with your clinician if you have a chronic health condition.
• If breathing training triggers severe dizziness, chest pain, or fainting, stop and seek medical attention. Hypocapnia from inappropriate hyperventilation techniques can be harmful; that’s why guided, paced slowing and professional programmes are safer than attempting extreme breath-holding or forced hyperventilation exercises. 

Conclusion

Many people habitually breathe in ways that raise sympathetic arousal and reduce vagal tone; dysfunctional breathing affects a meaningful minority of the population and is even more common in people with asthma or unexplained breathlessness. Training slow diaphragmatic breathing regularly is a low-risk, research-backed way to improve vagal tone, lower blood pressure and cortisol, reduce muscle tension (including jaw clenching), and protect cognitive and emotional resources from chronic over-arousal, but it takes practice and, for some people, guided help. 

References

1.Demeter, S.L. (1986) ‘Hyperventilation syndrome and asthma’, Chest, 89(3), pp. 388–392.

2. Deenstra, D.D., et al. (2022) ‘Prevalence of hyperventilation in patients with asthma’, ERJ Open Research, 8(1), Article 00520-2021.

3. Kaur, J., et al. (2018) ‘Regulation of regional cerebral blood flow during graded challenges: CO₂ and sympathetic interactions’, Journal of Applied Physiology, 125(2), pp. 301–310.

4. Obaya, H.E., et al. (2023) ‘Effect of aerobic exercise, slow deep breathing and mindfulness on cortisol’, Journal of Complementary and Integrative Medicine, 20(3).

5. Paccione, C.E., et al. (2022) ‘Meditation-based diaphragmatic breathing vs. vagus nerve stimulation: a randomized trial’, Applied Psychophysiology and Biofeedback, 47(4), pp. 317–329.

6. Polmann, H., et al. (2019) ‘Association between sleep bruxism and stress symptoms: a systematic review’, Journal of Oral Rehabilitation, 46(6), pp. 552–563.

7. Steffen, P.R., et al. (2017) ‘The impact of resonance frequency breathing on measures of heart rate variability, blood pressure and mood’, Frontiers in Public Health, 5, Article 222. https://doi.org/10.3389/fpubh.2017.00222

8. Thomas, M., McKinley, R.K., Freeman, E. and Foy, C. (2001) ‘Prevalence of dysfunctional breathing in patients treated for asthma in primary care: cross sectional survey’, BMJ, 322(7294), pp. 1098–1100. https://doi.org/10.1136/bmj.322.7294.1098

9. Tweeddale, P.M., Rowbottom, I. and McHardy, G.J.R. (1981) ‘Hyperventilation to induce bronchoconstriction in asthma’, Thorax, 36(8), pp. 580–584.

10. Vidotto, L.S., Carvalho, C.R.F., Harvey, A. and Jones, M. (2019) ‘Dysfunctional breathing: what do we know?’, Jornal Brasileiro de Pneumologia, 45(1), e20170347. https://doi.org/10.1590/1806-3713/e20170347