Every so often a new sports monitoring app catches me by surprise. As a Pixel Watch user, I have a weekly ChatGPT search scheduled for any developments in HRV or Bluetooth HRM for Wear OS. A few weeks ago I was pleasantly surprised by a chat notice that a "new-ish" app now supported Bluetooth HRV and DFA a1 for Wear OS (and the Apple watch).
The app is called Watchletic, and in this post we will take a quick peek at its ability to track DFA a1 during a sample indoor trainer session. Since the app is still in development and the DFA a1 implementation is still being fine tuned, no formal stats will be presented. However, in a future post, a more formal evaluation will be done. As usual, this is N=1 so YMMV.
The app was installed on my PW5 watch with no issues and pairing with a Polar H10 was quick. The screen interface is also straightforward to use to create custom fields on your watch:
Here is a screenshot of the entire session from my Fold 8:
As of now, there does not appear to be a way to change line color, but the recorded file is downloadable as a .fit file. That .fit file can be uploaded or analyzed as well, here is the file data as interpreted by Runalyze:
- It should be noted that the Runalyze file DFA a1 values/plot is derived from the RR output of the H10 (from the .fit file). I used that same .fit file for Kubios vs Watchletic a1 for the comparison.
The following 2 hour session was comprised of a warm-up, a submax ramp (up to my first threshold), and 5 sets of blood flow restriction (2 min on - 2 min off with compression at 75% AOP).
Since we have Runalyze on board, looking at the O2 sat drops through the BFR is always fun:
(Yeah, the first set had minimal O₂ desaturation.)
How did DFA a1 fare between the RRs analyzed with Kubios vs Watchletic?
Here is the entire 2 hours. The max artifact was 1% or less, so we don't have to be too concerned about the "better" Kubios automatic correction method.
A couple of comments before we zoom in to the ramp and BFR intervals:
- I struggled to align the output data due to some technical issues in Watchletic that will be addressed in an update. It's possible some of the deviation is related.
- The app does use Kubios detrending methodology and threshold artifact correction. However, there are some bug fixes in the next version that may change the outcome.
Zooming in to the ramp/intervals:
- This is the most encouraging image of the bunch. Why? It shows virtually identical dynamic range of a1 from high to low on the BFR intervals. It's been my experience that apps that don't do well vs Kubios have little issue in the 0.8 to 1.5 range but can't reach the low nadirs of the anticorrelated ranges below 0.5.
Yes, the ramp did show some deviation, and we will be following that carefully.
What else can the app do, HRV wise?
It also has the option of reporting RMSSD for those interested in resting HRV. It's still using 2 minute windows but can display the running average:
I am hoping to see the RMSSD (and artifact %) as a data field on the watch display.
Summary:
- Apple Watch and Wear OS users now have an option for DFA a1 display and RR recording while exercising. This is a very reasonable option to both display DFA a1 in real time, record RRs for later upload and show the session graphics on your phone afterward.
- For those interested in RMSSD, that is also available in the smartphone display (for now).
- So far the "agreement" with Kubios HRV is promising but still needs to be explored further.
Stay tuned for updates...
