What are HRV score, RMSSD, ln(RMSSD), SDNN 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 a more detailed analysis of their HRV data. Most app users will work solely with the HRV score and Readiness score, however, those working with a coach or practitioner may need the other metrics as described below. 

Here’s a quick rundown of what they mean (NN or R-R intervals means the time between two successive heartbeats):

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 the 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.

Please see this article for an overview of what these metrics correlate to: HRV Metrics and Norms

Did this answer your question? Thanks for the feedback There was a problem submitting your feedback. Please try again later.

Still need help? Contact Us Contact Us