Physiological Sigh vs Square Breathing

Techniques to Reduce Stress and Support Nervous System Regulation

Breathing is one of the simplest yet most powerful tools to manage stress, regulate the nervous system, and support overall well-being. Two effective techniques—physiological sighs and square breathing—offer distinct benefits and can be used together for a complete breathing practice.

What is the Physiological Sigh?

First discovered in the 1930s (Huberman Lab), the physiological sigh is a natural two-part inhale followed by a long exhale. When you deliberately use this breath, it interrupts the body’s threat system, calming your sympathetic nervous system and helping you self-soothe in moments of tension.

When we are stressed, we often under-breathe or breathe shallowly, which reduces oxygen intake and limits exhalation. This can increase carbon dioxide levels in the bloodstream and cause small lung sacs, called alveoli, to collapse. The physiological sigh works as a quick “reset,” fully inflating these alveoli and promoting relaxation. Think of it like releasing built-up energy—similar to the playful “zoomies” in animals—providing an immediate relief from tension.

What is Square Breathing?

Square breathing, sometimes called box breathing, is a foundational practice for daily stress management. It involves equal periods of inhalation, holding the breath in, exhalation, and pause (for example, in for 4, hold for 4, out for 4, pause for 4). 

Practicing this regularly strengthens overall breath control, supports calm focus, and improves nervous system regulation. This technique is best done consistently, much like taking a daily walk—it builds long-term resilience.

Using Physiological Sighs and Square Breathing Together

The two techniques complement each other:

• Physiological sighs act as a quick reset during high stress or rising tension.
• Square breathing builds daily resilience and long-term breath awareness.
  

For a practical routine:

• Begin with a physiological sigh to release tension.
• Transition to square breathing for longer-term calming and focus.
• Use throughout the day, before challenging meetings, social interactions, or before sleep.
  

Tips for Effective Breathwork:

• Take an extra deep inhale to fully expand the alveoli.
• Extend your exhale slightly longer than your inhale for a lopsided square breath (e.g., in for 4, hold for 4, out for 6–8, pause empty for 4).
• Treat each breath as a mini-meditation, or as we call them, “one-breath meditations,” to gently reset your nervous system throughout the day.
  

Breathing practices like these are simple, evidence-based ways to reduce stress, regulate the nervous system, and support mental and physical health.

To learn more about the physiological sigh, check out our blog: The Science of Physiological Sigh: Insights from Huberman Lab

Related Resources:

• EMDR Therapy for Trauma and Nervous System Regulation
• Cognitive Behavioral Therapy for Anxiety and Pain
• Mindfulness and Body Awareness Techniques such as Tapping and Emotional Freedom Techniques and Acceptance and Commitment Therapy.
• Access Resources: Check out our Trauma Blog for tips, exercises, and insights into managing mind-body challenges.

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References:

Huberman Lab – Ask Me Anything: Neuroscience with Andrew Huberman
How to Breathe Correctly for Optimal Health, Mood, Learning & Performance
Effect of breathwork on stress and mental health: A meta-analysis of randomised-controlled trials