The Physiological Sigh

What it is

Two inhales, one long exhale. Your body already does this spontaneously — after crying, during sleep, and periodically throughout the day without your involvement.

Doing it deliberately, a handful of times, is sometimes called cyclic sighing.

What it is doing in your nervous system

The lungs contain hundreds of millions of alveoli, the small sacs where gas exchange happens. During ordinary shallow breathing, particularly under stress, some of them collapse. A single ordinary inhale does not fully reopen them. The second, shorter in-breath does — it pops the collapsed sacs back open and restores surface area for gas exchange, which allows more efficient offloading of carbon dioxide on the exhale that follows.

The long exhale then does the vagal work described in extended exhale breathing: heart rate falls, vagal influence rises.

What makes this practice unusual is the trial evidence. A 2023 randomised study run at Stanford compared five minutes a day of cyclic sighing against box breathing, cyclic hyperventilation and mindfulness meditation, over a month. Cyclic sighing produced the greatest improvement in daily mood and the largest reduction in respiratory rate — outperforming an equivalent dose of mindfulness meditation.

Two things to hold alongside that. It was a single study with a healthy, largely self-selected sample, and it has not yet been broadly replicated. And "outperformed meditation on mood over a month at five minutes a day" is a claim about a specific comparison at a specific dose — not a claim that breathing beats meditation generally. It is still the best evidence in this library, and it deserves to be reported accurately rather than inflated.

When to use it

• In the seconds before you say something you will regret
• Mid-panic, when nothing longer is available to you
• Standing outside a room you are about to walk into
• When your chest is tight and your breath has gone high
• As a five-minute daily practice, which is the form the trial actually tested
• Any moment you have less than thirty seconds

When it is not the right practice

Rarely a problem, but a few notes. If you have asthma, COPD or another respiratory condition, check with your doctor and do not force the second inhale. Repeated too vigorously it can cause lightheadedness — it is a sigh, not a gulp. And speed is its strength and its limit: it changes the moment, not the pattern. If you are reaching for it fifteen times a day, the thing to look at is the load, not the breathing.

Where it sits in Soma Circuit

Level 5 of the Overwhelmed module, alongside running on the spot — a deliberate pairing of the fastest settling practice with the fastest discharge practice. Streaming audio.