What are R-R intervals?

Heart rate variability (HRV) is NOT heart rate. HRV is a powerful biomarker that has helped hundreds of thousands to:

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

Key to its power is HRV's deep connection to your nervous system, which controls and responds to many important body processes.

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

Fig 1: Heart rate variability

To measure HRV, you must have a compatible heart rate monitor that accurately senses RR-intervals. Many monitors do not meet this standard because:

  • They were not designed with HRV in mind, and do not have the required accuracy. Most wrist-wearables (watches, etc) fall into this category.
  • They record RR-intervals but artificially "smooth", average or alter them before transmitting to us. Our app tries to alert you when this happens with a reading.

Find a list of accurate heart rate monitors on our compatible devices page.

Learn more about HRV and how it ties to your Autonomic Nervous System.

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