How do you calculate the HRV score?
Our HRV score process is broken down as follows:
- We receive the R-R intervals directly from the chest strap heart rate monitor or CorSense device.
- Obvious artifacts are cleaned. The raw, unaltered R-R intervals are backed up securely to the server database. This allows us to improve algorithms for all current and past calculations, as well as for you to export the raw, unaltered R-R intervals if desired.
- We apply the RMSSD calculation to the R-R intervals. Root Mean Square of Successive Differences (RMSSD) is the industry standard time domain measurement for detecting Autonomic Nervous System (specifically Parasympathetic) activity in short-term measurements (5 minutes or less).
- A natural log (ln) is applied to RMSSD. RMSSD does not chart in a linear fashion, so it can be difficult to conceptualize the magnitude of changes as it rises and falls. Therefore, it is common practice in the application of RMSSD to apply a natural log to produce a number that behaves in a more linearly distributed fashion.
- The ln(RMSSD) is expanded to generate a useful 0 to 100 score. The ln(RMSSD) value typically ranges from 0 to 6.5. Using over 6,000,000 readings from our database, we have been able to sift out anomalous readings and create a much more accurate scale where everyone fits in a 0 to 100 range – even Olympians and elite endurance athletes.
During the reading, it is calculated on a rolling 15-second basis, so you can see the progression of your changing HRV during the reading.
The final HRV number in your reading results is calculated from all of the raw R-R data collected over the duration of the reading.
Notes on updates to the algorithm: When we've made changes to algorithms in the past, we strategically decided if we were going to back-update the calculated values.
If we deem it important (such as when we updated the artifact cleaning algorithms) then we will back-update historical values and have notified the users.