What are R-R intervals?

Heart rate variability (HRV) is NOT heart rate. Heart rate is just your average number of heartbeats, while HRV is the tiny difference BETWEEN each heartbeat.

Fig 1: Heart rate variability

HRV is a powerful biomarker that has helped millions to:

  • Improve training and recovery
  • Get fitter, faster, and stronger
  • Get healthier and address chronic disease
  • Manage stress
  • And much more!

Key to the power of HRV is its deep connection to your nervous system, which controls and responds to many important body processes, like:

  • Digestion
  • Respiration
  • Metabolism
  • Vision, hearing, and smell
  • Sexual function
  • and more

This connection requires tracking small changes (milliseconds) in the intervals between successive heartbeats (Fig 1 above), also called "R-R intervals". This is different from heart rate, which just averages the number of beats per minute.

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