Heart rate variability — variation in time between consecutive heartbeats. Interpretation depends on the metric, rhythm, person, and measurement context.
HRV reflects several interacting control systems, including breathing and autonomic input. Slow paced breathing near the cardiovascular resonance range often increases HRV during the session; that acute respiratory effect does not by itself prove a durable improvement in resting HRV or health.
See also
Glossary · Physiology
RSA (Respiratory Sinus Arrhythmia)
The normal variation in heart rate across the breath cycle — faster on inhale, slower on exhale.
Glossary · Physiology
Vagal tone
A functional description of parasympathetic cardiac modulation. It can be estimated in context, but is not directly read from one wearable score.
Learn · Science
HRV and Coherence Breathing: What the Research Shows
Heart rate variability rises when the breath is slow, steady, and near the cardiovascular resonance frequency. Here is the mechanism and the evidence.
Learn · Techniques
Coherence Breathing (5.5-5.5): The HRV-Peak Rhythm
Coherence breathing sits near 5.5 breaths per minute — within the common adult cardiovascular resonance range. It can raise in-session heart rate variability, although each person's exact resonance pace differs.