HRV breathing for iPhone and Apple Watch

Breathing, measured by your own heart.

A slow, guided breath you can follow with your eyes closed, and a live view of your heart answering it. Herz helps you find the pace your heart responds to most, then practise there.

Herz – Resonance BreathingiPhone and Apple Watch

Coming soon to the App Store

A session in Herz: the breathing stone in the middle of the screen, and beneath it a live heart-rate trace rising and falling with the breath, with the heart-rate swing, time in target, heart rate and Rhythm.

What resonance breathing is

Your heart already follows your breath.

Your heart rate is never quite steady. It rises a little as you breathe in and eases as you breathe out. The effect is always there; you just can’t feel it.

At one slow pace, the swing grows much larger. Breathing at that rate falls into step with one of the body’s own slow reflexes, the one that helps steady blood pressure, and the two reinforce each other. That pace is your resonance frequency. It differs from person to person.

Resonance breathing is simply practising at that pace, ten to twenty minutes at a time, and coming back to it over weeks.

4.5–7

Breaths per minute

Where most adults’ resonance pace lies. Yours is probably not exactly six.
10–20

Minutes a session

Long enough to settle in. The app offers five to twenty.
Weeks

Not one sitting

A single session is pleasant. What is worth having comes from repetition.

How the app works

A breath to follow, and a heart that answers.

The lower half of a session screen: a solid line, the heart rate, rising and falling with a faint dashed line, the breath; beneath it the heart-rate swing, the time in target, the heart rate and Rhythm.

01 · The session

Follow the stone

A pale stone fills with light as you breathe in and settles as you breathe out, slow enough to follow at the edge of vision. With an Apple Watch or a chest strap, your heart rate is drawn live against the breath, so you can see the moment the two fall into step.

Heart-rate swing is how far your heart rate rises and falls across one breath.
Rhythm, from 0 to 100, shows how much of your heart’s movement is happening at the pace you are being given.
Five to twenty minutes, at your pace and breath ratio: Equal, Gentle or Long out.

The assessment’s introduction, Find your resonance frequency: six paces of two minutes each with a minute of rest between, about seventeen minutes in all.

An assessment result: a resonance frequency of 5.8 breaths per minute with high confidence, a bar chart of the heart’s response at each pace peaking at 6, and a table of every pace measured.

02 · Finding your resonance

Find the pace that is yours

The assessment walks you through six paces, from seven breaths a minute down to four and a half, two minutes each with a minute of quiet rest between. It takes about seventeen minutes, once.

Your heart’s response at each pace is scored, and every pace is laid out in a table: swing, how closely your heart tracked the pacer, and more. The strongest becomes your training pace.
In each rest you note how the pace felt. If you feel lightheaded, say so: the assessment pauses and that pace is set aside.
Take it again on another day and the app settles on the middle of your results, not just the latest. The assessment needs a chest strap, which reports every beat.

The Progress screen: a week of practised days and the headline 8 days in a row, then a Rhythm score of 57 out of 100 over 30 days with a bar for each session, the heart-rate swing by session at 5.5 breaths a minute, and the resting baseline.

03 · Progress

Let it build

Progress is one calm scroll: the days you practised, how closely your heart followed the pace and the swing it made, then your resting baseline and your sessions. It grows over weeks rather than asking for a score on any one day.

Swing is charted at the pace you practise most, so sessions are compared like with like.
A resting baseline, a few still minutes with no pacing, is the one reading that can show change in you rather than in the skill. It needs a chest strap.
If you like, sessions are saved to Apple Health as mindful minutes.

Guidance in Settings: haptic guidance switched on, and the sound set to Ocean, with River, Wind and Off beside it.

04 · Sound and touch

Breathe with your eyes closed

Haptic swells rise in your palm through the in-breath and ease back through the out-breath. Add Ocean, River or Wind, and the sound swells around you as you breathe in and settles as you breathe out.

A singing bowl marks each turn: a bright one as you begin to breathe in, a warm, low one as you begin to breathe out.
Tap a sound in Settings to hear one breath of it.
Minimal mode strips the screen back to the stone.

Herz on Apple Watch: the breathing stone above a pace of 5.5 breaths a minute.

05 · Apple Watch

Your heart, read at your wrist

Wear an Apple Watch and its heart-rate reading is drawn on your iPhone as you breathe. The watch has the same breathing stone, so it can follow a session started on your phone, or run one on its own with the pace set by the Digital Crown.

The watch reports an averaged heart rate every few seconds rather than every beat, so beat-to-beat variability figures are left out rather than estimated.
A Bluetooth chest strap such as the Polar H10 reports every beat, for the full figures, the resting baseline and the assessment.

The Practice screen in the light look, Linen: an oat ground, charcoal type and the pace of 5.5 breaths per minute on a pale stone.

The same Practice screen in the dark look, Ember: a warm brown-black ground, ivory type and a honey-lit stone.

06 · Appearance

By day, and by night

Linen by day: an oat ground and charcoal ink. Ember by night: warm brown-black, lit with honey. Choose Light or Dark, follow your iPhone, or let Auto turn dark at sunset and light again at sunrise.

Auto works out sunrise and sunset on your iPhone from your approximate location, which is never sent anywhere. Without it, Auto is dark from 7 pm to 7 am.

Principles

Calm, private, and yours.

Calm

Nothing to chase

Slow light, soft sound, warm colour. No account, no feed and no ads. Just a breath to follow and a record that builds quietly.
Private

No one is watching

No analytics, no tracking, no advertising identifiers. The app makes no network connections of its own, so there is nothing to send us.
On device

It stays with you

Your sessions, readings and assessments live on your iPhone. Apple Health only receives mindful minutes, and only if you allow it. You can delete everything from Settings.

Every number in Herz is the heart’s response to the pace it was shown. When the signal can’t support a figure, the figure is left out rather than guessed.

A slower breath, and a heart that follows.