Understanding potential discrepancies between HRV values calculated by Hexoskin vs Kubios

As you may know, HRV values are automatically calculated by the Hexoskin for Rest and Sleep only. In fact, based on the literature, HRV values can only be accurately and meaningfully measured during a period with very minimal activity and movement.

If you wish to have HRV calculated in instances other than Rest and Sleep, you will have to export certain Hexoskin returned files into the Kubios software. But please note that movement can cause outliers in the ECG signal and then bias the HRV calculation and interpretation.

All the HRV metrics are very sensitive to outliers. Adding one or two irregular RR intervals may create a discrepancy of more than 45%. In the example below, there are about six missed heartbeats that Hexoskin doesn't include in the HRV calculations.

When you import data in Kubios, it recalculates all the RR intervals. Kubios will automatically include all heartbeats even the missed ones (rr_interval >1 sec, gray point on the example above) in its HRV calculations. If these missed heartbeats are included, it will bias the results. To avoid this in Kubios, you can remove these missed heartbeats by changing the "Beat correction" setting to "Threshold (medium)". By doing so, you will get the corrected RR intervals (blue line). This analysis should provide you with similar HRV values calculated by Hexoskin.

Overall, when doing HRV analyses, it is crucial to manually verify every RR interval data file to ensure that your calculations will not include outliers. If you do have some, you can remove them by adjusting the filters in Kubios.