hey Scott, here is an answer to my concern with your approach to DFA a1 testing from Bruce Rogers on youtube, he specifically addresses the approach you suggest and states he now uses the rolling window : HRV relevance to zone training - YouTube
Hope you find this helpful. The Runalyze program does this very nicely, you can download the FIT file then merge the HRV logger RR file and presto it gives you the ability to look at the DFA a1 with all sorts of options. you can select portions of a curve, vary the rolling window as you want, the over lap (the difference between window calculations ie 5 second rolling 2 minute window. Really quite nice and it does a lest squares fit through your power vs DFA a1 plot and suggests the aerobic threshold. I still think some care needs to be taken in cases where your DFA a1 bounces around a bit. It can cause the fit line to waver and I prefer to look for the first time it crosses the 0.75 line. Anyhow still learning but it is a cool option and seems to be gaining strength as a valid approach to the determination of the first break point.
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