What are HRV score, RMSSD, ln(RMSSD), SDNN, NN50, and PNN50?

Our HRV score is based on RMSSD and represents the strength of your Autonomic Nervous System (specifically the Parasympathetic branch) at a given time.  Click here for more information on average HRV scores in our community.

The other numbers provided are for reference for those interested in more detailed analysis of their HRV data.

Here’s a quick run down of what they mean (NN or R-R intervals means the time between two successive heart beats):

RMSSD: Root mean square of the successive differences – used for a good snapshot of the Autonomic Nervous System’s Parasympathetic branch and is the basis of our “HRV Score”

  • RMSSD is strongly backed by research and is considered the most relevant and accurate measure of Autonomic Nervous System activity over the short-term. Here are a few studies referencing its use:
  • More research about the use of RMSSD can usually be found on PubMed, ScienceDirect or other research libraries.

ln(RMSSD): A natural log is applied to the RMSSD in order to distribute the numbers in an easier to understand range

SDNN: Standard deviation of the NN (R-R) intervals

NN50: The number of pairs of successive NN (R-R) intervals that differ by more than 50 ms

PNN50: The proportion of NN50 divided by the total number of NN (R-R) intervals

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