So I am a PhD scientist (mathematical epidemiology) so I am used to reading papers, but I am not an exercise physiologist. Here are my thoughts:

The average VT1 GAS was 39.8 ml/kg/min (±8.9) compared to 40.1 ml/kg/min (±8.6) obtained by HRVT. The average HR at VT1 GAS was 152 bpm (±21) compared to 154 bpm (±20) obtained by HRVT. … Intraclass correlation between VT1 GAS and HRVT was 0.99 for VO2 and 0.96 for HR. The comparison of VT1 GAS and HRVT showed no differences (VO2: p = 0.347, d = 0.030; HR: p = 0.191, d = 0.091).

This is an incredibly strong correlation and unlikely to occur due to chance.

LIMITATIONS:

Seventeen male volunteers aged 19–52, without previous medical history, current medications or physical issues were tested.

The authors state pretty clearly my issue with this, and TBH, I’m surprised they were given IRB approval to do a study on only men, in medicine, this study would not get approved…

Although this study was done with a wide range of subject age and fitness characteristics, no female participants were tested. If the DFA a1 index behavior is to be considered as a zone 1 delimiter for the general population, further investigation using female subjects is mandatory.

Also, 17 participants is a very small sample size.

Participants did not consume caffeine, alcohol or any stimulant for the 24 h before testing.

I dont know enough about exercise physiology to know if this would be a problem, but I would assume that caffeine would impact the heart…

Another area of concern is the transfer of the DFA a1 0.75 breakpoint obtained during incremental testing to that of one found during constant load exercise, including moderate length intervals (5 min). No data is available comparing DFA a1 behavior during an incremental ramp to constant load exercise (Gronwald and Hoos, 2020), making automatic transfer of zone boundaries unclear.

Most people don’t only do constant load exercise, so I am concerned about this.

They list this as a limitation:

Another interesting subject to explore is the impact of athlete overtraining on DFA a1 behavior and VT1 prediction accuracy during exercise. Baumert et al. (2006) did show changes in DFA related scaling behavior after intense training, which may provide both a potential source of HRVT bias and an opportunity to screen for overtraining states.

But I wonder if thats not a limitation at all but a benefit.

Another area for investigation is whether DFA a1 cut off values are equivalent between chest belt and research grade ECG recordings. Although in this study, the RR intervals were recorded with a research grade ECG device, it may be possible to reproduce similar results with chest belt ECG recordings.

and

the question of DFA a1 value precision obtained by diverse monitoring devices possessing different sample rates and prepossessing strategies. Device sample rates have been shown to variably alter DFA a1 values at rest (Voss et al., 1996; Tapanainen et al., 1999; Singh et al., 2015) but may have more significant effects during exercise.

This seems to be a concern noted in the medium post:

The main challenge of this method seems to be getting high-quality data. Even the best chest straps out there (Polar H7 or H10), generate quite a few artifacts when running, often causing the following computations to be impacted.

and what concerns me is:

Currently, the only app that can compute DFA alpha 1 in real-time is the Heart Rate Variability Logger for iPhone and Android. … For these reasons, the HRV Logger allows you to employ an aggressive artifact removal strategy (“workout” mode under Settings).

My summary is: I think this is an interesting technology that if you have $10 that you don’t know what to do with, this seems like a cool way to spend it and do some N=1 experiments on. If multiple TFUA athletes use this app, I’d love to see a thread where people keep track of their drift test + lab test + HRV app test so we could start to gather some data.

I’ve used this app since February and find it interesting/useful/worthwhile. It took me a couple of runs to figure out how to configure the app/strap but once I did I’ve been using it as a rough proxy for my AeT.

I have found that:

* The DFAa1 .75 value correlated well (if a couple beats low) with the results of the 2 self administered lactate test I’ve done since February. Both lactate tests were done when I was fresh.

* DFAa1 Changed by a couple points almost every day – mostly reflected in how I was feeling.

* There’s an art to figuring how to use the data. Artifacts are an issue but you can download the data after the fact and see how many artifacts there are per two minute increment. (The app only gives you DFAa1 values in 2 minutes increments). I tended to disregard the interval if there were more than one or two artifacts.

* It was only good for consistent running. Because of the two minute reading interval, changes in pace under two minutes aren’t properly reflected in the readout.

* In my case, DFAa1 .75 heart rate value on flat ground is different than the .75 value uphill. Sometimes shockingly so. This alone makes me wonder what exactly is being measured based on my (limited) understanding of the concept.

But overall, despite the quirks, I’ve been using the app as a rough check in for a daily AeT. I think it saved me from a training mistake or two (when DFAa1 HR value tanked for a couple of days after a round of heavy training) and it gave me a good visual on exactly how much I had to warm up.

FWIW

Hi all! I decided to give this a try. I downloaded the app yesterday and used it on my run this morning with my Polar H9 cheststrap. Should mention that my strap has been giving me some grief lately – seems to lose connection mid run and my HR display will drop until it’s in the 60s. Going to submit a warranty claim today, most likely.

Anyway, chest strap did work pretty well for a while today and I figured I likely had some decent data. I opened up the excel file afterward and did find that 0.75 corresponded with 146 bpm (hr drift had put my aet in the low 150s). However, looking at the artifacts per reading, I don’t have any readings with fewer than 6 artifacts. Average of all my readings is 41 artifacts – seems very high! Especially considering what Al said about throwing out any with more than 2 artifacts. Could potentially be related to the issue with my strap?

I’m going to research about how to prevent artifacts and see about getting my cheststrap monitor looked at. Curious what others find!

Hi Brittany,

Sorry that happened to you but it sounds like the strap. But if it isn’t, and you’ve configured the app to the recommended settings, I recommend:

* checking to see if your strap how your strap is communicating with the app. Sometimes you can find an option to swap between a bluetooth and an ANT connection. You want the ANT connection.

* making sure that your running motion isn’t moving the strap too much. When you get deep in the weeds on the technology there’s some discussion on how some running motions lead to lower readings (by moving the strap). The solutions were to tighten the strap or to wear a rash guard/tight shirt to keep it from moving.

Good luck.

Nice catch Jon. It should be a bluetooth connection.

Brittany- Have you looked into connection VS sports bra? I find sports bras with wider bands move my HR monitor more than “light support” with a thin chest band.

Well, in that case the problem seems very clear! Hopefully polar fixes it for you!