What the physiological sigh is
A physiological sigh is a breath pattern with three parts. You take a full inhale through your nose. Then you take a short second inhale to top up your lungs. Then you let a long exhale out through your mouth. The double inhale opens more air sacs in the lungs, and the long exhale slows your breathing down.
Andrew Huberman's podcast made this pattern widely known. Researchers also call it cyclic sighing. The pattern is different from box breathing, which uses equal counts and holds, and from coherent breathing, which uses equal inhale and exhale at about five to six breaths a minute.
On this page the timer runs the pattern for you. You do not need to count in your head. The pacer shows when to inhale, when to add the short second inhale, and when to exhale.
What the research found
One randomized controlled trial tested cyclic sighing against other practices. The study ran for one month and took place remotely. It had 108 adults. Five minutes a day of cyclic sighing produced greater improvement in mood and a greater reduction in breathing rate than an equal period of mindfulness meditation [Balban et al. 2023].
The same trial compared cyclic sighing with box breathing and with cyclic hyperventilation with retention. Cyclic sighing showed the larger mood improvement [Balban et al. 2023]. The authors, Balban, Huberman, Spiegel and colleagues at Stanford, call daily cyclic sighing promising as a stress-management exercise.
This is one study. It ran remotely, and mood was self-reported. The senior author later became an advisor to a wearables company, which the paper discloses. One trial is not proof, and individual results vary.
Other slow-breathing research gives context. A 2018 systematic review of 15 studies in healthy people found slow breathing under 10 breaths a minute was associated with increased HRV and reports of relaxation [Zaccaro et al. 2018]. Those studies were small. A 2020 meta-analysis of 58 randomized controlled studies of HRV biofeedback found a small to moderate effect in its favour, largest for anxiety and depression, with each result based on a small number of studies [Lehrer et al. 2020]. These are associations from small or moderate studies, not proof.
How to use the timer
Set aside five minutes. Sit or lie comfortably. Breathe through your nose where you can, and let the exhale leave through your mouth. Keep the breath light and unforced. Over-breathing can cause light-headedness, so stop if you feel dizzy.
The timer paces the pattern for the full five minutes. Follow the pacer rather than counting. If the long exhale feels like too much at first, shorten it and build up over days.
Five minutes a day is the dose used in the Stanford trial [Balban et al. 2023]. If you want a longer practice, twenty minutes a day is the dose in Leah Lagos's program and in most HRV biofeedback studies [Lehrer et al. 2020].
You can also try the breathing pacer for other rates, the box breathing timer for equal counts with holds, or the resonance frequency test to find your personal slow rate.
A worked example
Suppose you want to practise at 5.5 breaths a minute, a common resonance rate. One breath takes 10.9 seconds. The inhale takes 4.4 seconds, and the exhale takes 6.5 seconds. In the physiological sigh, the first inhale and the short second inhale together fill that 4.4-second inhale window. The long exhale fills the 6.5 seconds. Five minutes at this rate is about 27 breaths.
Who should check with a clinician first
Anyone who is pregnant, has a heart or lung condition, a history of fainting, panic disorder, or epilepsy, or is being treated for a mental health condition should check with a clinician first. Slow breathing can lower blood pressure and heart rate. People on medication for either should ask their clinician. Nothing on this site is medical advice, a diagnosis or a treatment.
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