Breath is now widely recognized as a powerful tool for enhancing overall health. In Part 1 of our series, “Breath awareness in Yoga” we explored how different regions of the torso engage during breathing and how consciously engaging the abdominal and pelvic regions can provide numerous benefits, including lowering heart rate, reducing blood pressure, decreasing inflammation, and promoting relaxation.
However, when relating breath to health, focusing solely on which part of the body is involved is not enough to grasp its full complexity. Several key features of the breath itself must also be considered—specifically, its pace, rhythm, and smoothness.
In this Part 2, we will explore the crucial role of breath’s pace. Modern research is now uncovering the science behind optimal breathing rates and their critical role in overall well-being.
The speed or rate of breathing, usually measured in breaths per minute. The normal respiratory rate for healthy adults is approximately 12-20 breaths per minute, under normal conditions. However, this rate can vary depending on physical activity, stress levels, and emotional states.
Breathing rates above 20 breaths per minute—often a response to stress, anxiety, or physical overexertion—disrupt the balance of oxygen and carbon dioxide in the bloodstream. Chronic hyperventilation is the most commonly described and researched form of dysfunctional breathing (Boulding et al., 2016), and has been linked to various conditions such as anxiety, panic disorders, cardiovascular stress, chronic fatigue and weakened immune system. Over time, this habit reinforces a state of physiological imbalance, keeping the nervous system in a cycle of reactivity rather than resilience.
In the last two decades, an increasing number of studies have explored how consciously slowing down the breath—a practice often referred to as slow-paced breathing—benefit both the body and the mind. By intentionally reducing the respiratory rate, slow-paced breathing improves gas exchange in the lungs, enhances alveolar recruitment and expansion, and helps maintain optimal levels of oxygen and carbon dioxide.
This leads to improved ventilation efficiency and better oxygen delivery to tissues. But that’s not all—beyond the respiratory benefits, slowing the breath has also been shown to positively impact the cardiovascular and nervous systems, further contributing to overall health and well-being. Today, science has identified an optimal breathing rate of around 6 breaths per minute, which we explore in greater detail in the following sections.
To understand why the optimal breath pace is around 6 breaths per minute, it’s essential to first explore the important role the autonomic nervous system plays in the way breath supports health. The autonomic nervous system is divided into two key components:
Heart Rate Variability (HRV) is a key marker of how well the autonomic nervous system is working to regulate those various bodily functions. HRV measures the natural fluctuation in heartbeats. It’s a common misconception to think that the interval between successive heartbeats should be fixed. In reality, a healthy heart doesn’t beat like a metronome! Its rhythm is dynamic and constantly shifting, enabling the cardiovascular system to quickly adapt to sudden physical and psychological challenges to homeostasis (Shafferet al., 2014).
The brain constantly processes information in a region called the hypothalamus, which receives signals from the autonomic nervous system to instruct the body on whether to stimulate or relax various functions. When the body is in a fight-or-flight mode (sympathetic activation), the variation between heartbeats tends to be lower. In contrast, when the system is in a more relaxed state (parasympathetic activation), the variation between heartbeats tends to be higher.
Ideal HRV varies significantly based on factors such as age, fitness level, genetics, lifestyle, and health status. However, it is generally considered that within your normal range, a higher HRV is better, as it indicates a more adaptable and resilient autonomic nervous system. A decrease in HRV is associated with a higher risk of cardiovascular events and mortality (Fang et al., 2020), chronic stress (Immanuel et al., 2023), affective disorders (Siepmann et al., 2022), and neurological conditions (Arakaki et al., 2023). HRV is therefore recognised as a key marker of health, reflecting the balance between sympathetic and parasympathetic regulation, and provides valuable insights into overall health and resilience.
There are different ways to measure HRV, with the two most commonly used being time domain and frequency domain analyses.
Time-domain measures of HRV are the most straightforward to calculate and assess the variation in time between successive heartbeats, also known as interbeat intervals or RR intervals. These measures provide insight into the overall variability and balance of the autonomic nervous system. However, they do not differentiate between the underlying physiological mechanisms that contribute to HRV. To gain deeper insight into these mechanisms, frequency domain analysis is used.
Frequency domain analysis breaks down HRV into different frequency ranges (Shaffer et al., 2014), each representing specific physiological processes:
Typical HRV recording over a 15-minute period under resting conditions in a healthy individual. The top trace represents the original HRV waveform, while the lower traces show the separated frequency bands: Very Low Frequency (VLF), Low Frequency (LF), and High Frequency (HF), obtained through filtering techniques (Shafferet al., 2014). Reproduced from Shaffer et al. (2014), under CC BY 4.0.
As we discussed above, higher HRV is generally a sign of better health and resilience. Recent research has uncovered an optimal breathing frequency that maximizes HRV, known as Resonance Breathing. This peak frequency typically occurs around 0.1 Hz, which is equivalent to about 6 breaths per minute. However, the resonance frequency can vary between individuals, typically falling between 4.5 and 6.5 breaths per minute.
Slow-paced breathing at a resonance frequency of around 6 breaths per minute has been linked to numerous health benefits, including improved cardiovascular function (enhanced heart rhythm regulation and blood pressure reduction), better oxygen saturation, increased maximal oxygen consumption (VO₂max), and enhanced physical performance. It may also contribute to reductions in muscle weakness, oxidative stress, and inflammation (Sevoz-Couche et al., 2022)
Maximum HRV is typically observed at about a respiratory frequency of 6 breaths per min (0.1 Hz). Adapted from Bernardi et al. (2001)
Just as pushing a swing at the right moment increases its amplitude, slowing the breath to about 6 breaths per minute synchronizes the respiratory, cardiac, and blood pressure rhythms, creating a harmonious synergy in your body known as “resonance” (Russo et al., 2017; Sevoz-Couche et al., 2022). Today, science understands that the effect of slow-paced breathing on HRV is primarily mediated by the vagus nerve through the following mechanisms:
Increasing Respiratory Sinus Arrhythmia (RSA)
You may recall from the previous section that RSA is reflected in the High Frequency (HF) band of HRV and refers to the natural variation in heart rate during the breathing cycle. During inhalation, vagal activity decreases, causing the heart rate to rise, while during exhalation, vagal activity is restored, leading to a decrease in heart rate. At around 6 breaths per minute, the timing of inhalation and exhalation optimizes the balance between the sympathetic (activating) and parasympathetic (relaxing) branches of the autonomic nervous system. This enhances HRV and creates pronounced oscillations in the heart rate.
Enhancing Baroreflex Function
The baroreflex is a feedback mechanism that helps regulate blood pressure by adjusting heart rate. For example, when blood pressure rises, the baroreflex slows the heart rate to restore balance. Breathing induces rhythmic fluctuations in intrathoracic pressure, which, in turn, affects blood pressure. During inhalation, intrathoracic pressure decreases, temporarily reducing venous return to the heart and lowering blood pressure. In response, the baroreflex increases heart rate to compensate.
During exhalation, intrathoracic pressure increases, enhancing venous return and raising blood pressure. The baroreflex then responds by decreasing the heart rate. Slowing the breath to about 6 breaths per minute amplifies these fluctuations in thoracic pressure and blood pressure. The larger oscillations in blood pressure activate baroreceptors more intensely, which enhances the sensitivity and efficiency of the baroreflex. This results in more pronounced and synchronized oscillations in low-frequency (LF) band of HRV.
Maximizing parasympathetic activity
The parasympathetic nervous system, primarily through the vagus nerve, slows the heart by releasing acetylcholine, which reduces heart rate. In contrast, the sympathetic system speeds up the heart rate through the release of norepinephrine. The parasympathetic system typically responds faster due to quicker signal transmission.
Acetylcholine also inhibits norepinephrine release, allowing the parasympathetic system to dominate heart rate regulation at rest. Slow, deep breathing enhances vagal stimulation, increasing the release of acetylcholine and strengthening the parasympathetic influence on the heart. This leads to a more flexible and adaptable heart rate, characterized by pronounced oscillations that reflect a healthy balance between the sympathetic and parasympathetic nervous systems.
From a physiological perspective, breathing at frequencies below 0.1 Hz disrupts the optimal synchronization between respiratory, cardiac, and blood pressure rhythms that typically occurs during resonance breathing, leading to a decrease in heart rate variability (HRV). Despite this, the effects of breathing at such slow rates have been largely overlooked in the scientific literature.
One key reason is that very slow breathing, without proper training, can feel unnatural, uncomfortable, and difficult for most people to achieve. Consequently, studies exploring this phenomenon have primarily focused on advanced practitioners, such as experienced yogis and Zen monks.
Studies on advanced yoga and Zen practitioners have shown that very slow breathing around 1 breath per minute, reduce heart rate and result in a shift from resonance in the low-frequency (LF) range to the very low-frequency (VLF) range (Lehreret al., 1999; Jovanov et al., 2005). Participants also reported an increased feeling of internal warmth during the breathing. The shift toward very low frequencies may indicate that the body prioritises other regulatory mechanisms, such as thermoregulation, metabolic adjustments, or deep states of autonomic withdrawal, similar to hibernation-like states observed in advanced meditation.
Research on Zen practitioners further suggests that very slow breathing influences central nervous system activity. Sessions of voluntary slow diaphragmatic breathing around 3-4 breaths per minute, increased EEG alpha power and decreased EEG theta power (Fumoto et al., 2004; Yu et al., 2011). These neural shifts are consistently associated with enhanced mental states, including greater energy and alertness, as well as reductions in anxiety, depression, anger, and confusion.
Together, these findings indicate that breathing at extremely slow rates induces profound physiological and psychological changes, potentially unlocking deeper states of autonomic regulation and mental well-being. However, more research is needed to fully understand the implications and long-term effects of breathing at frequencies below 0.1 Hz.
Taken together, these findings suggest that vagal activation is the key mechanism behind the physical and mental health benefits of slow breathing. The good news? You don’t need to slow your breath to extremes to experience these effects. Simply maintaining a steady pace of around 6 breaths per minute is enough to create an optimal physiological state, supporting autonomic balance and overall well-being.
But that doesn’t mean the journey stops here. As you become more comfortable with slow breathing, exploring even deeper levels may uncover new layers of physiological and mental transformation—opening the door to enhanced self-regulation, profound changes in both body and mind, and heightened awareness.
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