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If you are like most exercisers, you breathe through your mouth, especially as the intensity of the exercise increases. However, experts are learning that breathing through the mouth may not be as efficient, or effective, as breathing through the nose.

The nose is built with a specific purpose: to support our respiratory system. The primary purpose of the mouth, on the other hand, is to start the digestive process. The nostrils, hair, and nasal passageways are designed to assist in filtering allergens and foreign bodies from entering the lungs. The nose also adds moisture and warmth to inhaled air for smoother entry to the lungs.

Nasal breathing, as opposed to mouth breathing, has another important advantage, especially for effective and efficient exercise: it can allow for more oxygen to get to active tissues. This is because breathing through the nose releases nitric oxide, which is necessary to increase carbon dioxide (CO2) in the blood, which, in turn, is what releases oxygen. Mouth breathing does not effectively release nitric oxide, which means the cells are not getting as much oxygen as through nasal breathing, which could lead to fatigue and stress.

A recent study demonstrated this. The study tested 10 runners, both male and female, who for six months had been utilizing nasal-only breathing while exercising. Participants were put through standardized testing, once with nasal breathing and then with mouth breathing, to compare their maximum oxygen intake rates. They were also tested for various other respiratory and exercise markers, including oxygen and carbon dioxide levels while exercising.

Their maximum rate of oxygen consumption did not change from nasal to mouth breathing. But the study found that the runners’ respiratory rate, breaths per minute, and ratio of oxygen intake to carbon dioxide output decreased during nasal breathing. The researchers said this is probably because of the lower breath rate used during nasal breathing, which allows more time for oxygen to get to the bloodstream.

Hyperventilation through the mouth causes the body to offload more CO2, making it harder to oxygenate our cells. In intense moments, nasal breathing is the ideal way to oxygenate our systems.

Nasal breathing also activates the part of the nervous system that supports rest, recovery and digestion (parasympathetic), rather than the part of the nervous system that is responsible for survival or stress states (sympathetic). This means that, even if the body is in a stressful state of high-intensity exercise, nasal breathing can provide a sense of calm and allow us to function better.

As demands of physical activity increase, athletes may switch from breathing nasally to oronasally, or to breathing completely orally. Performance can, however, be inhibited by nasal breathing at the point when exertion becomes very intense. Oral breathing occurs in shallow, quick breaths in order to receive more oxygen (O2) into the lungs and higher carbon dioxide (CO2) into the body. At higher intensities of physical activity, nasal breathing cannot provide the volume of O2 that oral breathing can, and less O2 content will result in a decrease in athletic performance. On the other hand, while mouth breathing at high levels of exertions may result in hyperventilation, nasal breathing effectively reduces this state. The evidence, thus, still supports nasal breathing, even at higher levels of performance, as a more efficient mode, given that the same amount of mechanical work is completed at a lower metabolic cost compared with oral respiration.

The Physiological Mechanisms

Respiration is a fundamental physiological process and finding the most efficient breathing mode during exercise warrants further exploration. Breathing, or ventilation, is the process of gas exchange from the outside environment to the alveoli. For optimal athletic performance, the goal is to utilize oxygen (O2) as efficiently as possible.

Mouth breathing syndrome (MBS) is characterized by inhaling and exhaling primarily through the mouth and is considered to be an abnormal respiratory function. MBS is a pathology that is associated with the obstruction of the upper airways and increased resistance of nasal breathing. Prolonged mouth breathing can lead to muscular and postural alterations. Consequently, the habit of breathing through the mouth, even without obstruction, alters the balance of facial muscles and causes facial skeletal changes.

Many healthcare professionals are unaware of the negative effects of MBS and that MBS can lead to changes in tongue and head position. With MBS, the location of tongue is down and backwards instead of up and forward in the palate. The tongue position influences the palatal development and can cause a forward head position. Every inch of forward head posture increases the weight of the head on the spine by approximately 10 pounds creating an adverse load on the cervical joints, induced by poor spinal, cervical, and scapular postures. Additionally, the forward head position may strain the deep postural-stabilizing muscles of the spine, reducing the performance of their functional postural-supporting role.

A significant problem with MBS is the reduction of oxygen absorption leading to a downward spiraling effect on sleep, stamina, and energy levels.

Mouth breathing causes biochemical, physiological, and immunological disturbances. Among the biochemical and physiological disorders related to MBS are lower oxygen absorption (chronic hypoxemia), increased CO2 concentration (hypercapnia), and changes in the acid-base balance, towards respiratory acidosis. Mouth breathing is also associated with increased water loss, and decreased energy.

Additionally, mouth breathing can cause changes in sleep patterns, which can contribute to a decrease in immune defense cells and an increase in humoral serum values related to inflammatory mediators, indicating the occurrence of oxidative stress and an altered systemic inflammatory state. A reduction in the quality (or quantity) of sleep can result in biological and cognitive imbalance, potentially decreasing physical performance and the recovery process after a workout.

The nose has numerous functions: olfaction, sensation, mucociliary clearance, filtration, and immunological functions. In addition, the nose has the function of regulating and humidifying the air during the nasal cycles of airflow dynamics. Nasal breathing cleans the air as it enters the body, produces nitric oxide (NO), and performs the same amount of work with less energy expended. Immunological functions of the nose produce mucus and secrete immunoglobulins. The nose has its own self-defense due to its coarse hairs and the secretions it creates. In addition, the nose protects the lungs from allergens and other bacteria through its immunologic properties.

As ambient oxygen (O2) passes through the sinuses, it diffuses across the nasal epithelium and can be used by the cells to produce NO. As the sinuses produces NO and air is continuously inhaled, NO reaches the lungs and is diffused into the capillaries of the surrounding alveoli, expanding vessels and increasing O2/CO2 exchange. The powerful vasodilating effects of NO lead to increased oxygen uptake, a reduction in pulmonary vascular resistance, and arterial oxygenation.

The benefits of enhanced NO productivity include increased aerobic capacity, reduced hypertension, increased insulin sensitivity and glucose tolerance, capillarization and angiogenesis, and even long-term potentiation associated with cellular models for learning and memory. An additional benefit of enhanced NO productivity is neurogenesis, which is the process by which new neurons form in the brain.

Nitric oxide, through nasal breathing, regulates autonomic functions like heart rate, respiration, blood pressure, and digestion along with mood, sleep cycle, fluid balance, and reproduction. The increase of blood flow derived from NO synthesis may improve recovery processes as well.

So, if nasal breathing helps us stay relaxed and improves our athletic performance, how can we do more of it?

First, pay attention. Do you more often breathe through your nose or mouth during the day? What about while exercising, especially as the workouts get more difficult? Notice what is happening with the breath as well as what it feels like to pay attention to the breath.

Now consider practicing nasal breathing. Close the mouth and relax the tongue and jaw. Start by simply nasal breathing during warm-ups and cool downs with workouts. Then try experiencing daily life while breathing through the nose. Some people who mouth breathe during sleep try “mouth taping,” putting specially designed tape over their lips to assist with nasal breathing.

Once you have your groove and are consistently nasal breathing, check for potential differences in these areas.

  • Emotional state — Nasal breathing should lead to a more relaxed state. When life is stressful, and you note that you are mouth breathing, try switching to nasal breathing and inhaling slowly and deeply.

  • Exercise performance — At first, high-intensity exercise may feel more difficult with nasal breathing. The body needs to adapt to a different approach to the respiratory process, and if it is used to hyperventilation during exercise, nasal breathing may feel a bit slow at first. Things will shift. Be patient.

  • Exercise recovery — Because nasal breathing is more efficient, recovery should be smoother.

  • Immune system — Nasal breathing is a major line of defense against airborne pathogens. The mouth has no defense system. You may experience improvements with overall breathing and decreasing allergies or colds.

"Our breath is the direct link to a calm, clear, mind and body.”



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