Matt's Blog on HRV4 & DFa1 | 80/20 Endurance

Matt’s Blog on HRV4 & DFa1

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  • #13397

    If you haven’t read it, it’s here:

    Heart Rate Variability

    So, I’ve been using the DFA1 protocol for about 6 months now, in fact I specifically bought a certain HRM (Polar H9) in order to do the regular testing as my regular HRM (Scosche Rhythm24) did not yield results despite supposedly supporting HRV.

    My test results were almost without exception always quite a bit lower than what I *thought* my AeT or Ventilatory Threshold was based on other testing (low 130s bpm vs mid 140s). Not sure why that is but curiously the test results were pretty consistent with what MAF tells my I should use as a AeT/VT ceiling (i.e. low 130s).

    Anyway, what I am most curious about is if it’s possible to add DFA1 to the 8020 Garmin IQ datafield? We can currently show 8020 zones in Pace/Power/HR but it seems to me that it would be most helpful to see DFA1 live and in real time. There are a few CIQ developers out there adding DFA1 to their datafields but so far all I’ve seen are applicable only to Garmin cycling devices (like the Edge) and not my FR 945.


    Matt Fitzgerald

    We’re going to discuss this internally in our next company meeting.


    Neat, thanks Matt.


    Hold the phone, I’m not so sure it would be all that useful to have as a data field.

    I did a few outdoor tests using my Polar H9 (a few truly easy runs and 1 cycle) and in reviewing Runalyze’s DFA1 graph after the fact, the results were very mixed.

    The cycle seemed to indicate DFA1 might offer a good way for thresholds as at no point on my bike (an easy 60min spin in 93 degree “feels like” conditions) did I pass the threshold, only briefly touching it in spots.

    But both runs were well under the .75 threshold for all but the points when I took a break (to let my dogs cool off in a creek). Both of these runs felt easy RPE-wise and HR was in check as well. But DFA1 would indicate I was well over my Aerobic Threshold the entire time.


    I agree, some of these variables are not appropriate for real-time tracking. Nevertheless, collecting the information is valuable.

    I am currently following the 80/20 Level II 10K Run Plan. My Garmin 945 suggested workout today (from First Beat) was a Base Workout because I had a restless sleep yesterday, and my 80/20 Plan called for a Fartlek RFR44. I did the 80/20 suggestion because Garmin does not know my goal to run a 10K race in 9 weeks and I believe it was the correct decision, I hit my paces and feel I will recover before the next key workout.

    My point is that we are on the cusp of a real paradigm shift because of this emerging technology. 80/20 has hinted about the integration AI Technology. I am hopeful that they will share in their plans and articles how we can best utilize the technology as it become available.


    I also enjoyed the article and it pushed me to finally get a HRM. I ended up going Tickr X because it was on sale (and the features), hoping the HRV app would still work with it.

    I have only worn jt three times but haven’t yet gotten the metrics I was hoping for. It pairs with my watch but doesn’t record gps data, cadence, or anything else – just HR.

    Does anyone have experience with the Tickr X? Specifically with a Garmin 935 watch? Can you get it to measure cadence and all the other stats? I have an email into their help dept. too and thought to seek wisdom in here as well ;-).

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