HRV & COHERENCE
Heart rate variability is the closest thing
we have to a real-time readout of resilience
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.
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 but measure something slightly different.
What the numbers mean: What the numbers mean if you're wondering how to improve heart rate variability: there's no universal "good" HRV. Your baseline is yours. What matters is the trend over time, the variability of the variability (how much your HRV fluctuates day to day), and how quickly it recovers after stressors. A rising 7-day average suggests improving regulatory capacity. A declining trend or reduced variability often precedes burnout, illness, or overtraining.
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 synchronise
Cardiac coherence is a specific state where the pattern of heart rate variability becomes smooth and ordered — a sine-wave-like rhythm at approximately 0.1 Hz (about 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 creative thinking), reduced cortisol, increased DHEA, and measurably better emotional regulation. Coherence training doesn't just feel calming — it changes the physiological conditions in which your brain operates.
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.
MCCRATY & CHILDRE, HEARTMATH RESEARCH CENTER, 2010
Respiratory sinus arrhythmia training at resonance frequency improved vagal tone and stress resilience in high-demand professionals.
LABORDE ET AL., PSYCHOPHYSIOLOGY, 2022
TRAINING HRV
What actually moves the needle
Breathing rate training: Breathing at your resonance frequency (typically 4.5–6.5 breaths per minute) is the single most effective way to improve HRV acutely and, with practice, at baseline. This is the foundation.
CO₂ tolerance work: Improving your system's comfort with carbon dioxide reduces the overbreathing pattern that suppresses HRV. These two practices — breathing rate and CO₂ tolerance — reinforce each other.
Sleep: HRV is most trainable through sleep quality. Nasal breathing during sleep (often supported by mouth taping after proper assessment) significantly improves overnight 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 — even 5 minutes twice daily — produces measurable improvements in resting HRV within 4–6 weeks.