Heart Rate Variability (HRV)

The VX Sport system now supports Heart Rate Variability tracking (HRV) for both live and post analysis. HRV is the fluctuation of time between adjacent heartbeats and is generally measured in milliseconds. Fluctuations in HRV can show changes in stress level - and thus can be a useful tool when working with high performance athletes or those subject to stressful conditions. HRV values are non-comparable between different people and are affected by many different factors.


How is HRV measured?

Heart beats are complex, non-linear and fluctuate with stimulus from the autonomic nervous system. HRV analysis requires accurate measurement of the variability of the interbeat interval (IBI), which is the time period between consecutive heartbeats - also referred to as RR Intervals. We can use these RR intervals to calculate time domain indices for use during specific tests and tracking longitudinally.


The measures offered by the VX Sport system include:


  • RMSSD - (Root Mean Square of Successive Differences). The RMSSD reflects the beat-to-beat variance in heart rate and is the primary time-domain measure used to estimate the vagally mediated changes reflected in HRV.
  • SDNN - SDNN is the standard deviation of the IBI of normal sinus beats and is measured in milliseconds. "Normal" means that abnormal beats, like ectopic beats, have been removed.


The VX Sport system allows users to track and view Heart Rate Variability data in a number of ways - including:

  • Post download summary data
  • Beat by beat HRV data export 
  • Live HRV Tracking with up to 40 athletes
  • Streaming Live data to VX Live-Stream


For more information on Heart Rate Variability check out the webinar we held with Dr. Angela Spontelli Gisselman:



To learn more about how the VX Sport system can help you get the best out of your athletes, contact us at

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