Health & Fitness · Glossary
What is Heart Rate Variability?
Quick definition
The variation in time between heartbeats, measured in milliseconds. A marker of recovery and overall health.
Full explanation
Heart Rate Variability (HRV) is the variation in time between consecutive heartbeats (R-R intervals). A higher HRV generally indicates better cardiovascular fitness and recovery status. Low HRV is associated with stress, poor sleep, illness, and overtraining. HRV is measured with chest straps or some smartwatches. It is best tracked as a personal trend over time, not compared to others. HRV drops after intense exercise, alcohol, illness, and stress — and rises with good sleep, moderate exercise, and recovery. Used by athletes to time workouts, by biohackers to track readiness, and clinically as a cardiovascular risk marker.
Related calculators
Calculators that use or explain Heart Rate Variability.
Related terms
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Last reviewed: June 15, 2026 • Category: Health & Fitness