A breathing practice · est. 2026
Calmence is a science‑led breathing practice built around your resonance frequency — the one pace, typically near 0.1 Hz1, where heart, lungs, and vascular rhythm fall into a single slow wave. No gamification. No guilt streaks. Just the oldest nervous‑system tool you own, finally made precise.
The science
In adults, it typically lies between 4.5 and 6.5 breaths per minute 17. Breathe at that pace and heart rate, blood pressure, and respiration synchronize into a single standing wave. This is not folk wisdom — it is a property of the baroreflex system 2.
The baroreflex stabilizes blood pressure via baroreceptors in the aorta and carotid arteries signaling through the vagus nerve 7. At ~0.1 Hz, breathing stimulates this closed loop at its natural period — amplifying heart‑rate oscillations roughly 4–10× over resting baselines 1.
When you inhale, the cardiovascular centre inhibits vagal firing and heart rate accelerates; when you exhale, vagal inhibition is restored and heart rate slows 7. Slow paced breathing increases cardiac vagal tone, indexed by LF power and RMSSD 7.
Respiratory Sinus Arrhythmia (RSA) is the healthy swing of heart rate across a breath, mediated by the vagus nerve 7. RSA amplitude increases with slower breathing and is the primary training target in HRV biofeedback 3.
Heart rate and blood pressure oscillations at the resonance frequency strengthen the baroreflex — the homeostatic system that regulates blood pressure.
The practice
A Calmence session is a single moving sphere that rises on your inhale and falls on your exhale. Calmence reads your resting HRV from Apple Health or Android Health Connect after sessions, and shows a 7-day trend on the Insights tab.
A six‑minute assessment sweeps across candidate rates — 4.5 / 5.0 / 5.5 / 6.0 / 6.5 breaths per minute — the exact protocol described by Lehrer and colleagues 7. Your pace. Not an average.
No counting, no narration. The sphere expands for your inhale, settles for your exhale. At 0.1 Hz, heart rate and breathing synchronize (0° phase), producing maximal HRV amplitude 1.
If you wear an Apple Watch or Android wearable, Calmence pulls your resting HRV from Apple Health or Health Connect and charts a 7-day trend. HRV reflects weeks of practice, not single sessions.
Sessions end in silence. A brief affect check — calmer, same, more wound‑up — and you're done. The best nervous‑system tool is one that stays out of the way.
Dosing
The effects above (blood pressure, baroreflex sensitivity, anxiety reduction) show up at specific dose ranges across the literature. Here is what the protocols in those studies actually asked participants to do.
Enough for roughly sixty resonance‑frequency breaths. Lehrer et al. typically prescribe 10–20 minutes per session at the assessed rate 23.
Twice daily is the most common cadence in clinical trials — once on waking, once in the evening. One session still produces acute effects 9.
Resting blood pressure reductions in meta‑analyses appear after roughly four weeks of ≥10 min/day slow breathing 510.
Shifts in resting HRV and baroreflex sensitivity — the carry‑over effects that remain when you aren't breathing with the pacer — typically emerge around six to ten weeks 3.
Evidence
We do not make claims Calmence cannot back with primary literature. Hover or tap any stat for its source. Effect sizes shown are from peer‑reviewed clinical trials and meta‑analyses in HRV biofeedback and slow breathing.
Gain in heart‑rate oscillation amplitude during resonance breathing vs. resting baseline.
Vaschillo, Vaschillo & Lehrer · Appl Psychophysiol Biofeedback · 2006 ↗
Pooled reduction in resting systolic blood pressure in published trials of slow-breathing protocols (≤10 breaths/min, ≥4 weeks), across 17 RCTs. Not a Calmence product claim.
Chaddha et al. · Am J Hypertension · 2019 ↗
Improvement in arterial baroreflex sensitivity after 4 weeks of slow breathing in hypertensive adults.
Joseph et al. · Hypertension · 2005 ↗
Large effect of HRV biofeedback on self‑reported stress and anxiety — meta‑analysis of 24 studies.
Goessl, Curtiss & Hofmann · Psychol Med · 2017 ↗
Most common coherence frequency, observed across 1.8 million HRV biofeedback sessions worldwide.
McCraty et al. · Scientific Reports · 2025 ↗
Range of adult resonance frequencies in breaths/minute — the window Calmence's assessment sweeps.
Shaffer & Meehan · Front Neurosci · 2020 ↗
Not another breathing app
Most apps loop a generic 4‑7‑8 or box‑breath timer at a one‑size‑fits‑all pace. Calmence implements the Lehrer‑Vaschillo protocol 27 — an individualized, measured practice. The difference is physiological, not stylistic.
Your first session
Open the app. Tap once. By breath nine you'll be inside a resonance the literature measures — no onboarding carousel, no signup to start.
No account. No onboarding survey. The app opens to the pacer. Tap once to begin.
The orb expands over five seconds, then settles over five. Breathe with it. That's the entire instruction.
By the sixth breath most people are matched to the pacer. Resting HRV shifts over weeks of practice, not within a single session.
Stay for ten more minutes. Steffen et al. measured HRV, BP, and mood changes after a single 15‑min resonance session 9 — sustained change builds from ~4 weeks of daily practice.
Voices from the field
Real stories land here after our closed beta. We'd rather leave this space empty than fill it with stock photos and invented quotes.
Who it's for
HRV biofeedback and resonance breathing have shown benefit in anxiety 4, hypertension 510, and clinical populations including asthma and depression 3. The underlying physiology does not discriminate.
A meta‑analysis of 24 studies found a large effect (Hedges' g ≈ 0.83) of HRV biofeedback on stress and anxiety 4.
A structured resonance‑frequency protocol with exportable coherence reports — the same assessment described by Shaffer & Meehan 7.
Parasympathetic reserve is a measurable edge. RF breathing has been applied across athletic and performance settings 3.
A daily practice the autonomic system can learn to trust again — complementary to, never a substitute for, medical care.
Pricing
You can run a real session today, for free. If Calmence becomes part of your week, upgrade. If not, the free tier stays the free tier — no throttled breaths, no paywalled pacer.
Forever. Not a trial.
Annual $59.99 · Lifetime $149 · 7-day free trial.
Questions