The physiological sigh (and a simpler way to get the same calm)

A physiological sigh is two inhales through your nose, one long and one short "topping off" sniff right on top of it, followed by one long, slow exhale through your mouth. In a month-long Stanford study, five minutes a day of it improved mood more than an equal dose of mindfulness meditation, though both eased anxiety by a similar amount (Balban et al., Cell Reports Medicine, 2023).

You may have done something like it without thinking about it. It can feel like the double-inhale hitch that sometimes happens before you finally exhale during a good cry, or the breath you take right before you drift off. Researchers gave it a name and studied what it actually does, and it turns out you can trigger it on purpose.

How to do a physiological sigh

Try it yourself

Double Exhale

Free to use, no account needed. A simpler one-breath version of the same idea: a long exhale tells your body it's safe.

Breathe in through your nose. Before you exhale, take a second, shorter inhale on top of it, filling your lungs a little further. Then let it all out in one long, slow exhale through your mouth, longer than both inhales combined. That's one round. One to three rounds is usually enough.

Why the physiological sigh works

The double inhale re-inflates tiny air sacs in your lungs, called alveoli. They collapse gradually during ordinary breathing, and the body normally reinflates them with an occasional spontaneous sigh, something that happens more often under stress (Li et al., Nature, 2016). Reopening them helps your lungs exchange oxygen and carbon dioxide more efficiently. The long exhale that follows is what does the calming work: a slow, extended out-breath leans on the vagus nerve, the main channel of your parasympathetic nervous system, and is linked to a lower heart rate (Zaccaro et al., Frontiers in Human Neuroscience, 2018). The Stanford researchers behind the cyclic sighing trial are honest that the exact mechanism is still an open question, and they found no significant difference in heart-rate variability between the breathing techniques they tested.

Physiological sigh vs Solace's Double Exhale

Solace's guided Double Exhale pattern times a single inhale for four seconds and a single exhale for eight, not the two-inhale version above. The reason is simple: a single breath is easier to follow along to with your eyes closed, and it relies on the same longer-exhale principle that makes the physiological sigh work.

If you want the full technique, do your own double inhale, then start the guide and let its count carry the long exhale. Either way, the lever being pulled is the same one: a longer breath out than in, telling your body the alarm can stand down.

When to use it

Right before something stressful, in the middle of a wave of anxiety, or anywhere you need a reset and don't have time for a longer practice. It's quiet enough to do at a desk or in a waiting room without anyone noticing. If anxiety shows up often rather than as a single stressful moment, Solace's breathing tools offer a few paced patterns worth trying, and grounding is worth a go too when a sigh alone doesn't settle things. For more on the broader picture, see how to calm your nervous system.

Sources

• Balban, M.Y., Neri, E., Kogon, M.M., et al. (2023). Brief structured respiration practices enhance mood and reduce physiological arousal. Cell Reports Medicine, 4(1), 100895
• Li, P., Janczewski, W.A., Yackle, K., et al. (2016). The peptidergic control circuit for sighing. Nature, 530, 293-297
• Zaccaro, A., Piarulli, A., Laurino, M., et al. (2018). How breath-control can change your life: A systematic review on psycho-physiological correlates of slow breathing. Frontiers in Human Neuroscience, 12, 353

This is not medical advice. If anxiety is frequent or affecting your daily life, it is worth speaking with a doctor or a qualified professional.