DFA a1 — aerobic threshold (top of Zone 2) from your heart rate

Automatically estimate your aerobic threshold (the top of Zone 2) from your ride data using DFA a1, a metric derived from your heart-rate variability. It's the boundary that decides how much easy endurance work you should be doing, and the hardest one to pin down without a lab test.

With a heart-rate chest strap and the AlphaHRV app, IntervalCoach would read this value after your rides and use it to sharpen your Zone 2 and tailor your workouts more precisely.

(Aerobic threshold / LT1 only for now, not a replacement for your FTP.)