The Oxygen Myth: Fast and Slow Breathing

The Oxygen Myth: Fast and Slow Breathing

(Chapter from the book “Being Centered” by Madeline Black)

Normal resting respiratory rate is between 10–14 breaths per minute. The body takes in oxygen, performs gas exchange in the lungs, and expels carbon dioxide. Under normal conditions, blood oxygen saturation is high: 97–87% at sea level, and around 95% at altitude. Approximately 75% of inhaled oxygen is returned to the atmosphere unused. Even during maximum exertion, about 25% of inhaled air remains unutilized (Chaitow et al., 2014).

This oxygen reserve is not easily accessed for a good reason—oxygen and carbon dioxide balance is essential for health, especially for the brain and heart. Oxygen consumption fluctuates in response to muscle activity, metabolism, and heart rate. Breathing rate is regulated to match the body’s needs (gas levels in blood and pH balance), ensuring stable oxygen supply to the brain and heart.

It’s actually the level of carbon dioxide (CO₂) in the blood—not oxygen—that regulates breathing. When activity increases, CO₂ levels rise, and the body demands more oxygen, prompting faster breathing. Conversely, during rest, breathing slows, CO₂ levels drop, and oxygen demand decreases.

Intentional over-breathing to take in more oxygen or to blow off CO₂ is a myth—especially regarding oxygen delivery to the brain and heart tissues.

Some instructors claim that rapid, rhythmic breathing—such as in Pilates’ “Hundred” exercise or fast yogic breathing—increases oxygen levels. It doesn’t. Rapid breathing floods the lungs with air, lowering CO₂ levels in the lungs. This leads the body to pull more CO₂ from the bloodstream.

But low CO₂ levels can be dangerous—they disrupt the normal pH balance, impairing oxygen delivery to tissues. Cells may stop releasing oxygen. The body reacts with a protective mechanism: the smooth muscles of cerebral blood vessels constrict, limiting blood supply to the brain. This results in physical symptoms like dizziness, tingling in extremities, and paleness.

In fact, fast breathing decreases oxygen delivery to the brain. It also stimulates the nervous system, heightening alertness or even euphoria—especially if the focus is on exhalation. But these sensations stem from CO₂ reduction and nerve stimulation, not increased oxygen.

Slow breathing has the opposite effect and is considered therapeutic. It strengthens emotional resilience. For example, yogic ujjayi breathing emphasizes slow inhales and exhales in a 1:2 ratio.

Elevated CO₂ levels promote vasodilation in the brain, increasing oxygen delivery. This leads to calmness, heightened awareness, and clarity. Practices like singing, monotone speech, and chanting help regulate and train slow breathing.

Slow breathing calms the nervous system and enhances blood oxygenation (Bernardi et al., 2001). It’s crucial to remember: fast breathing reduces, and slow breathing increases blood flow to the brain, without overburdening the cardiovascular system.

In his book “Return to Life Through Contrology” (1945), Joseph Pilates described the “Hundred” exercise with slow breathing, not the fast tempo often seen today. He emphasized “squeezing every atom of air out of the lungs until they are practically empty like a vacuum.” He also warned that excess oxygen intake may cause dizziness—not because of oxygen itself, but due to CO₂ reduction, leading to blood vessel constriction and reduced cerebral blood flow.

With slow breathing practice, complete exhalation and inhalation without hyperventilation will improve brain blood flow balance, increase mental clarity, and support a strong sense of wellbeing.