Saturday, May 15, 2021

DFA a1 - Runalyze vs Kubios vs Logger results in a cyclist

 See also -
Best practices for Runalyze and DFA a1 thresholds 

Since more data is always helpful in method comparisons, I'm killing two birds with one post - presenting a cyclist's data (who asked me to review his files) and taking the opportunity to see how our three options for DFA a1 analysis perform.  The recordings were done with a Garmin watch, HRV logger and a Polar H10.  The Runalyze output was set for a recalculation every 5 secs (like Kubios).

After a brief ramp to just beyond the AeT, additional cycling at varying intensity was done.  After matching up the time stamps and synchronizing the cycling power, the following graphs were done.

Entire ride session, DFA a1 over time:

The similarity in a1 readings appear quite good in all three methods.  I was very impressed with the agreement of Runalyze and Logger to Kubios

There are 2 areas of unexplained drop in Runalyze a1 data (blue circles).  This is explained by excess artifact, shown below in the Kubios view, using medium threshold correction.  The Kubios output above used the "auto" correction method (only in premium version) and the HRV logger used a very aggressive "work out mode" that were able to avoid this.

A zoomed look at the ramp, with power overlay:

Although Kubios (blue) appears to read a bit lower than either Runalyze (red) or Logger (black), they are close and the HRVT measures out about 5 watts different - very acceptable.

Plot of Ramp HR to DFA a1:

There was a bit more discrepancy with HR between Kubios and Runalyze in terms of HR.  Given the point scatter, not unexpected.  In addition, the test really did not get to an intensity where a1 reached .5, making interpretation subject to more error.


  • Both Runalyze and HRV logger in their current forms are approaching values seen with Kubios  software.
  • Given the price, PC footprint and time needed to do all these graphs, the Runalyze implementation is an attractive option for retrospective analysis.  Accuracy can be affected by artifact - beware of sharp changes in a1 for no reason
  • For real time estimation of a1, HRV logger is an excellent choice in terms of accuracy, price and convenience.

Heart rate variability during dynamic exercise

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