What is HRV? (Heart Rate Variability)
Heart Rate Variability (HRV) is the variation in time between heartbeats (RR intervals). Higher HRV generally reflects a more adaptable autonomic nervous system.
How it’s measured
- RMSSD: Root Mean Square of Successive Differences. A common short‑term metric sensitive to parasympathetic activity.
- SDNN: Standard Deviation of NN intervals. Reflects overall variability over the window.
Metrics can vary with window length, posture, time of day, and preprocessing (artifact removal).
What affects HRV
- Sleep quality, sleep debt, and circadian rhythm
- Psychological stress and recovery
- Illness, dehydration, alcohol
- Training load and overreaching
How to improve HRV (habits)
- Consistent sleep schedule and daylight exposure
- Breathing practices (e.g., coherence, box breathing)
- Moderate training with rest days
- Hydration and reduced late‑night alcohol
Educational only. Not medical advice.
Try a quick practice now: 2‑minute coherence session.