Yes, while you are doing them: slow breathing at about six breaths a minute makes your heart speed up and slow down with each breath, and HRV rises sharply during the exercise. Regular practice is also linked to higher resting HRV, but that longer-term change is smaller in the evidence and less certain.
What happens while you breathe slowly
Your heart rate already rises a little when you breathe in and falls when you breathe out. This is called respiratory sinus arrhythmia Respiratory sinus arrhythmia The normal rise in heart rate as you breathe in and fall as you breathe out. It is driven by the vagus nerve and makes up much of resting HRV. More about Respiratory sinus arrhythmia . Most people breathe 9 to 24 times a minute, and at those rates the swings are small.
When you slow down to about six breaths a minute, two things line up. Your heart rate rises and falls in step with your breathing. At the same time, the reflex that keeps your blood pressure steady starts to push in the same rhythm. Lehrer and Gevirtz, who reviewed this research, describe the heart rate swings growing to many times their size at rest. They say this happens in almost everyone, often within a minute, even on the first try. The best rate differs a little from person to person, and their research put the average nearer 5.5 breaths a minute.
The same review adds a caution. It notes that slower breathing and longer out-breaths can make these swings bigger on their own, possibly without any change in the vagus nerve Vagus nerve The main nerve of the parasympathetic nervous system, running from the brainstem to the heart, lungs and gut. Its fast signals to the heart drive most beat-to-beat HRV. More about Vagus nerve ’s activity. So a very high HRV during the exercise mostly shows the exercise working. It does not show that your resting HRV has changed.
Does it raise your HRV for longer?
Probably a little, but the evidence is thinner. A 2022 review by Laborde and colleagues pooled 223 studies of slow breathing. It found higher vagus-linked HRV during the breathing (172 studies), right after a single session (16 studies) and after programmes of repeated practice (49 studies). The authors concluded that slow breathing is a low-cost habit with few side effects expected.
Keep your hopes realistic. In a study of 28,175 people who measured their HRV each morning, age, sex, body mass index and activity level together explained only 15% of the differences in HRV between people. The authors pointed to genes and age as major drivers and suggested that aiming for a higher HRV may not be realistic for many people. Breathing practice may help you feel calmer and may nudge your numbers, but expect a small change in your baseline Baseline Your own usual HRV level and range, built from weeks of readings taken the same way. Comparing a reading with your baseline says more than comparing it with other people. More about Baseline at most.
How to try it
- Sit comfortably somewhere quiet.
- Follow the pacer above: about 4 seconds in and 6 seconds out, which makes six breaths a minute. A slightly longer out-breath is fine.
- Breathe gently, not deeply. If you feel light-headed, return to normal breathing.
- Start with a few minutes and build up if you like it.
To see whether regular practice changes your resting numbers, keep measuring the usual way at the usual time, never during the exercise. After a few weeks, compare your seven-day average with your average before you started.
For how stress and the nervous system affect HRV, see HRV and stress and does anxiety lower HRV?. For other habits worth trying, see how can I increase my HRV?
When to check with a doctor
Slow breathing is safe for most people. If you have a heart or lung condition, or breathing exercises make you dizzy or anxious, ask your doctor or a trained therapist before you practise regularly. Breathing exercises can support treatment for anxiety but should not replace it.