HRV & COHERENCE
Heart rate variability gives us a real-time glimpse of how well the body adapts to stress
Your heart doesn't beat like a metronome. The variation between beats reflects your nervous system's capacity to adapt. Higher variability, measured correctly, signals a system that can respond to demands and recover efficiently.
THE BASICS
Not your heart rate. The variation between beats.
Heart rate tells you how fast your heart is beating. Heart rate variability (HRV) tells you something more useful: how well your autonomic nervous system is balancing activation and recovery.
When your sympathetic nervous system dominates (stress, threat, high demand), the intervals between heartbeats become more uniform — your heart beats like a drum machine. When your parasympathetic system is engaged (safety, recovery, restoration), the intervals vary more — your heart responds flexibly to each breath, each moment.
Higher HRV generally indicates a nervous system with greater adaptive capacity. Lower HRV suggests a system stuck in a narrower range of response — often sympathetic dominance. This is measurable, trackable, and trainable.
PRACTICAL MEASUREMENT
What to track and how to make sense of it
Wearables that work: WHOOP, Oura Ring, Garmin (newer models), and Apple Watch (Series 4+) all provide HRV data. The gold standard for clinical measurement is a chest strap (Polar H10) with dedicated software, but for ongoing tracking a wrist-based wearable is sufficient. We review your wearable data as part of the breathing assessment.
When to measure: Morning HRV (taken within 5 minutes of waking, before getting out of bed) gives the most consistent baseline. Night-time averages from wearables that track continuously are also useful — they show how your system recovers during sleep, which is related to but distinct from your waking baseline.
What the numbers mean: There's no universal "good" HRV. Your baseline is yours. What matters is the trend over time, how much your HRV fluctuates from day to day (sometimes called the variability of the variability), and how quickly it recovers after stressors. A rising 7-day average suggests your system is moving in the right direction.
The key metric: RMSSD (root mean square of successive differences) is the most commonly used time-domain measure. Most wearables report this or a derivative. Don't get lost in the numbers — track the direction.
THE HEARTMATH MODEL
When your heart rhythm, breathing, and nervous system align
Cardiac coherence is a specific state where your heart rate variability becomes smooth and rhythmic — a gentle wave pattern that appears when your heart, breathing, and nervous system are all working in sync. It typically happens at a breathing rate of around 6 breaths per minute.
In this state, your heart, respiratory system, and autonomic nervous system are working in synchrony rather than competing.
The HeartMath Institute has spent three decades researching this state and developing tools to train it. Their model uses real-time biofeedback: you see your heart rhythm on screen and learn to shift it into coherence using a combination of breathing rate, emotional regulation, and focused attention.
What coherence produces: Improved cognitive function (particularly decision-making and sustained attention), reduced cortisol, and measurably better emotional regulation. These effects have been demonstrated in HeartMath's research and confirmed by independent studies.
How I use it: HeartMath biofeedback is one tool within the broader regulation framework. For some clients, seeing their heart rhythm respond in real time to breathing and emotional state is the thing that makes the entire approach concrete. It moves regulation from concept to visible, measurable practice.
Heart rhythm coherence facilitates cortical function, including attention, memory, and emotional processing.
Respiratory sinus arrhythmia training at resonance frequency improved vagal tone and stress resilience in high-demand professionals.
TRAINING HRV
What actually moves the needle
Breathing rate training: Breathing at your resonance frequency (typically 4.5–6.5 breaths per minute) is one of the most effective ways to improve HRV acutely and, with consistent practice, at baseline. This is the foundation.
CO₂ tolerance work: Training your body to tolerate normal levels of CO₂ — rather than triggering the urge to breathe too early — reduces the overbreathing pattern that suppresses HRV. These two practices — breathing rate and CO₂ tolerance — reinforce each other.
Sleep: HRV is strongly influenced by sleep quality — and research shows the relationship is bidirectional. Better sleep supports higher resting HRV, and better HRV supports more restorative sleep. Nasal breathing during sleep (often supported by mouth taping after proper assessment) improves overnight breathing patterns and HRV recovery.
Exercise: Moderate aerobic exercise improves vagal tone over time. Overtraining suppresses it. HRV tracking helps you find the balance.
Coherence practice: Regular HeartMath or resonance frequency breathing practice — sustained over weeks — produces measurable improvements in resting HRV. Research supports daily practice of 10–20 minutes as a benchmark (Ma et al., 2017: 15 min, twice daily, 8 weeks), though even shorter sessions build the skill when practised consistently. The 60-second practice on the homepage is a taste of this, and coherence practice is part of every week of Resilience Training.