Does Nose or Mouth Breathing Work Better for Exercise?

Jenn Hoskins
17th July, 2025

Does Nose or Mouth Breathing Work Better for Exercise?

This schematic outlines the randomized crossover protocol used to compare standard, exclusively oral, partial nasal, and exclusively nasal breathing conditions, facilitating the study's conclusion that nasal-only respiration significantly impairs peak exercise capacity.

Image adapted from: Mapelli et al. / CC BY (Source)

Key Findings

  • A study by scientists in Italy found that breathing only through the nose during intense exercise significantly lowered peak performance and oxygen use
  • This exclusive nasal breathing made the exercise feel much harder and restricted the body's ability to efficiently move air, limiting overall peak capacity
  • However, breathing through the mouth or a combination of nose and mouth did not hinder peak performance, suggesting these methods are more efficient for maximal effort
Breathing is fundamental to exercise, yet the optimal way to breathe during physical activity, particularly at high intensities, remains a subject of scientific inquiry. While some advocate for nasal breathing due to its filtering and humidifying benefits, the impact of different breathing modes on peak athletic performance has been less clear. Understanding this is crucial for athletes and anyone aiming to maximize their exercise efficiency. Recent research conducted by scientists from Centro Cardiologico Monzino, U. Milan, and U. Porto set out to clarify the most effective breathing strategy during various stages of maximal exercise[1]. They aimed to determine if exclusively nasal breathing, or breathing through the mouth, offered advantages or disadvantages during intense physical exertion. To investigate this, twelve healthy young adults participated in a series of Cardiopulmonary Exercise Tests (CPETs). A CPET is a sophisticated assessment that measures how the heart and lungs respond to increasing levels of physical activity. It provides a comprehensive picture of an individual's aerobic capacity and overall fitness. In this study, participants performed four different CPETs on a stationary bike: one under standard breathing conditions, one exclusively using nasal breathing (eNAS), one exclusively using oral breathing (eOR), and one with partial nasal breathing (pNAS) where one nostril was blocked. All tests were completed within a month to ensure consistency. The findings revealed significant differences, particularly when comparing exclusively nasal breathing to the other modes. The study showed that when subjects breathed only through their nose, they experienced a notable reduction in their peak oxygen uptake (peakVO2) and peak carbon dioxide production (peakVCO2). Oxygen uptake (VO2) is the amount of oxygen the body uses, while carbon dioxide production (VCO2) is the amount of carbon dioxide exhaled; both are key indicators of metabolic activity during exercise. Furthermore, peak minute ventilation (the total air breathed in and out per minute) and respiratory rate (breaths per minute) were also lower with exclusively nasal breathing. Participants also reported a higher perceived effort, as measured by the Borg scale, across all phases of the exercise when breathing exclusively through their nose. The Borg scale is a simple numerical rating system that allows individuals to self-assess their exertion level. This indicates that nasal breathing, while potentially beneficial for filtering air, made the exercise feel significantly harder. The study also noted that inspiratory and expiratory times (the duration of inhaling and exhaling) were longer, and resting lung function measures like forced expiratory volume (FEV) and vital capacity (VC) were reduced with exclusively nasal breathing. FEV measures how much air a person can exhale during a forced breath, and VC is the maximum amount of air a person can exhale after a maximum inhalation; both are indicators of lung capacity. These results suggest that exclusively nasal breathing during high-intensity exercise leads to a "ventilatory limitation". This means that the body's ability to move air in and out of the lungs efficiently is restricted, preventing it from reaching its full potential in terms of oxygen delivery and carbon dioxide removal, even if the body's demand for oxygen is met. Interestingly, only minor differences were observed at rest or at the anaerobic threshold (AT). The anaerobic threshold is the point during exercise where the body starts producing energy without enough oxygen, leading to a build-up of lactic acid and increased fatigue. These findings align with and expand upon previous research concerning factors that impede breathing during exercise. For instance, a separate study involving 71 healthy individuals investigated the impact of wearing surgical masks during exercise[2]. That research also utilized CPETs and found that wearing a mask led to "undesirable" performance, with participants reporting a higher Borg scale of perceived exertion[2]. Similar to the nasal breathing study, mask-wearing resulted in lower oxygen uptake and carbon dioxide production, especially at peak exercise, and the anaerobic threshold was reached earlier[2]. Breathing patterns were also altered, with longer inspiratory and expiratory times and reduced respiratory frequency and minute ventilation[2]. A crucial commonality between both studies is the observation that despite the reduced performance and increased perceived effort, percutaneous oxygen saturation (SpO2) remained stable when wearing a mask[2]. While the recent study on breathing modes did not explicitly report on SpO2, its conclusion of "ventilatory limitation" rather than a direct oxygen deficit suggests a similar compensatory mechanism. This indicates that the body is still able to take in enough oxygen, but it has to work much harder to do so when airflow is restricted, whether by a mask or by the narrower passages of exclusive nasal breathing. In essence, both studies highlight that any factor that restricts airflow – be it an external barrier like a mask or an internal physiological choice like exclusive nasal breathing – can negatively impact peak exercise capacity by imposing a ventilatory limitation. While nasal breathing may offer advantages for lower-intensity, steady-state activities, the recent research from Centro Cardiologico Monzino, U. Milan, and U. Porto strongly suggests that for achieving maximal performance during high-intensity exercise, the wider, less restrictive pathway of oral breathing, or a combination, is more efficient. This understanding provides valuable guidance for individuals seeking to optimize their breathing strategies during varying intensities of physical activity.

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References

Main Study

1) Nasal vs. oral BREATHing WIn Strategies in healthy individuals during cardiorespiratory Exercise testing (BreathWISE)

Published 16th July, 2025

https://doi.org/10.1371/journal.pone.0326661

Related Studies

2) Effect of Surgical Masks on Cardiopulmonary Function in Healthy Young Subjects: A Crossover Study.

https://doi.org/10.3389/fphys.2021.710573


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