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### What is DFA-alpha1?

Using the exact RR intervals between the individual heartbeats, the so-called DFA-alpha1 values are determined using non-linear mathematical methods. DFA stands for “Detrended fluctuation analysis” and alpha1 is the short term scaling exponent. It is known that this value changes with increasing intensity. From initial values above 1.0, the value decreases to about 0.75 at the aerobic threshold (not to be confused with the anaerobic threshold or lactate threshold!) and values around 0.5 at high intensity.

Where do I find the values?

In the activity view, in the heart rate variability section, you will find a link to aerobic threshold estimation, where the DFA-a1 values are displayed. Alternatively, you can find the link in the Tools dropdown of the activity (magic icon).

Premium users can also select and analyze HRV(-DFA-a1) values in the Trend Analysis and ANOVA tools.

How can I add RR data to an activity?

For thecalcu