The Biology of Breathing

Before diving into different breathing techniques, it helps to understand what's happening in your body when you breathe.

When you inhale, your diaphragm (the dome-shaped muscle below your lungs) contracts and moves downward, creating space for your lungs to expand. This expansion decreases pressure in your chest cavity, drawing air into your lungs. When you exhale, your diaphragm relaxes, moving upward and forcing air out of your lungs.

When practicing breathwork, it is recommended to use diaphragmatic breathing (also called "belly breathing" or "deep breathing"). Diaphragmatic breathers engage their diaphragm rather than using their chest muscles. According to a 2023 study in the Journal of Medical Internet Research, diaphragmatic breathing improves focus and reduces anxiety by activating the vagus nerve, which plays a central role in the parasympathetic nervous system.

But breathing does far more than just exchange oxygen and carbon dioxide. Your breath has a direct impact on your nervous system, particularly through something called respiratory sinus arrhythmia (RSA).

RSA is the natural variation in heart rate that occurs during the breathing cycle. When you inhale, your heart rate slightly increases; when you exhale, it slightly decreases. This connection between breath and heart rate is one way breathing exercises can influence your autonomic nervous system—the system that controls involuntary bodily functions.

The Autonomic Nervous System Connection

Your autonomic nervous system has two main branches:

1. Sympathetic nervous system (SNS): Often called "fight-or-flight," this activates during stress or danger
2. Parasympathetic nervous system (PNS): The "rest-and-digest" system that promotes relaxation and recovery

When you're stressed, your sympathetic nervous system dominates, increasing heart rate, blood pressure, and stress hormones. Controlled breathing can activate your parasympathetic nervous system, countering these effects and promoting relaxation.

Research by Zaccaro et al. (2018) found that slow breathing techniques (less than 10 breaths per minute) can increase parasympathetic activity and heart rate variability while decreasing sympathetic dominance and stress responses. Their research demonstrated that slow breathing techniques promote autonomic changes that increase Heart Rate Variability and Respiratory Sinus Arrhythmia, resulting in increased comfort, relaxation, and pleasantness, as well as reduced symptoms of anxiety, depression, arousal, and anger. 

Box Breathing (4-4-4-4)

Box breathing involves inhaling for 4 seconds, holding for 4 seconds, exhaling for 4 seconds, and holding again for 4 seconds before repeating. ZenSei users can tap into this powerful pattern using the green mode. 

This technique, also known as "square breathing," is used by everyone from Navy SEALs operating at peak performance to regular folks managing their anxiety. A 2018 study by Ma et al. found that similar controlled breathing exercises decreased the body's cortisol levels (a primary stress hormone) and improved feelings of comfort and relaxation.

4-7-8 Breathing

Popularized by Dr. Andrew Weil, this technique involves inhaling quietly through your nose for 4 seconds, holding your breath for 7 seconds, and exhaling completely through your mouth for 8 seconds. 

Research published in Frontiers in Psychology (2017) indicated that breathing techniques like 4-7-8 significantly improved heart rate variability, suggesting better stress regulation and parasympathetic activity. Popular before sleep, ZenSei users can use the white mode to try out this pattern. 

Sudarshan Kriya Breathing (4-4-6-2)

Sudarshan Kriya is a rhythmic breathing technique that involves inhaling for 4 seconds, holding for 4 seconds, exhaling for 6 seconds, and holding empty for 2 seconds.

Brown and Gerbarg (2019) examined how Sudarshan Kriya breathing could be integrated into psychiatric care. Their research found that Sudarshan Kriya breathing significantly improved outcomes for anxiety, depression, and PTSD. The physiological benefits included increased parasympathetic activity and reduced inflammation—effects that persisted even weeks after the intervention.

A seminal study by Brown and Gerbarg (2005) on Sudarshan Kriya breathing found that this specific breathing pattern activates the vagus nerve, shifts the autonomic nervous system toward parasympathetic dominance, and reduces symptoms of stress, anxiety, and depression. The researchers noted that the specific 4-4-6-2 pattern seems to create a unique physiological state that supports emotional regulation and mental clarity.

This powerful breath mode is available to ZenSei users in the blue breathing pattern. 

Four-Six Breathing

This simple technique involves inhaling for a count of four and exhaling for a count of six. The longer exhale than inhale is crucial for its effectiveness. Unlike the patterns we have encountered thus far, there are no holds. 

Research by Van Diest et al. (2014) found that breathing patterns with longer exhalations, like Four-Six breathing, produced greater heart rate variability, stronger parasympathetic activation, and higher self-reported relaxation compared to balanced breathing patterns. This makes Four-Six breathing an excellent starting point for beginners who may find more complex patterns challenging. ZenSei users can give this breathing mode a try using the orange breathing mode. 

Resonant Breathing (5.5-6 breaths per minute)

Resonant breathing, or coherent breathing, typically involves breathing at a rate of about 5.5-6 breaths per minute (inhaling and exhaling for approximately 5.5 seconds each). Like in Four-Six breathing, there are no holds. 

Resonant frequency breathing is hypothesized to improve heart rate variability. A 2017 study by Steffen et al. found that resonant breathing had significant positive effects on heart rate variability and mood, supporting its use for stress reduction and emotional regulation. You can tap into this soothing, even breath mode using your ZenSei in the yellow breathing mode. 

The Science Behind Why These Techniques Work

Heart Rate Variability (HRV)

Many breathing techniques aim to improve heart rate variability—the variation in time between successive heartbeats. Higher HRV is associated with better cardiovascular health, more effective stress regulation, and improved emotional well-being.

Research by Gevirtz (2020) concluded that controlled breathing exercises are among the most effective non-invasive methods for improving HRV. Heart rate variability (HRV) is a psychophysiological marker for physical and mental health and high HRV is an indicator of a healthy heart with more flexibility to react to stress, whether physiological or environmental.

Vagal Tone

The vagus nerve is the main component of the parasympathetic nervous system. "Vagal tone" refers to the activity of this nerve, with higher vagal tone associated with better stress resilience and emotional regulation.

According to Gerritsen and Band (2018), slow, deep breathing directly stimulates the vagus nerve, increasing vagal tone and promoting relaxation.

CO₂ Sensitivity

Your body's sensitivity to carbon dioxide levels plays a role in anxiety disorders. Hyperventilation (rapid breathing) reduces CO₂ levels, which can trigger anxiety symptoms in sensitive individuals.

Research by Russo et al. (2017) found that regular practice of slow breathing techniques can recalibrate CO₂ sensitivity, potentially reducing anxiety symptoms. Slow breathing can reduce alveolar dead space and ensure optimal gas exchange for oxygen richer breaths. This in turn can trigger the parasympathetic nervous system to reduce feelings of stress.

Brain Wave Activity

EEG studies have shown that certain breathing patterns can alter brain wave activity, promoting states conducive to relaxation, focus, or creativity.

A 2018 study by Zaccaro and colleagues found that slow breathing increased alpha wave activity in the brain, which is associated with relaxation and reduced anxiety.

Drawbacks of Smartphone Apps

Smartphones are often a source of stress in our day-to-day lives. They hold our unanswered emails and messages. For many, they are a necessary evil of working and living modern society. 

In recent years, there has been a rise in mindfulness apps like Headspace and Calm. These services offer videos and other guides for practicing mindfulness, meditation, and breathwork. Per a 2024 study by Callahan et al, there is evidence that these apps can result in a lower perceived stress (as measured by PSS-10). However, as demonstrated by Lam et. al in 2023, there is a marked retention problem. 

Many users sign up with positive intentions, but quickly stop using the app due to privacy concerns, complexity, cost, and technical issues. There’s nothing more frustrating than sitting down for a breathwork session and being interrupted by a call or a phone crashing. That’s why unconnected devices like ZenSei are growing in popularity as an alternative for those looking to explore breathwork!

Benefits Beyond Stress Reduction

Improved Cognitive Performance

Research by Chandla et al. (2013) found that regular practice of rhythmic breathing techniques improved attention, working memory, and cognitive flexibility. These improvements were measurable after just 8 weeks of daily practice.

Enhanced Immune Function

A 2019 study published in the Journal of Translational Medicine demonstrated that controlled breathing exercises increased the production of anti-inflammatory cytokines and reduced markers of chronic inflammation, suggesting potential immune benefits.

Better Sleep Quality

According to research by Jerath et al. (2018), slow breathing practices before bedtime improved multiple measures of sleep quality, including time to fall asleep, number of awakenings, and subjective sleep satisfaction.

Pain Management

A 2020 meta-analysis published in Pain Medicine found that breathing techniques were effective for reducing both acute and chronic pain, possibly through multiple mechanisms including reduced muscle tension and altered perception of pain signals.