Training
Heart rate zones
The Karvonen formula builds zones from your heart rate reserve (HRmax − HRrest), so it reflects your actual fitness rather than just your age. It is the most sensible way to set zones without a lab test.
The Karvonen formula
Target HR = HRrest + (HRmax − HRrest) × %intensity. If you do not know HRmax from a test, 220 − age is fine to start; measure resting heart rate in the morning, still in bed, over a few days and average it.
In the app: Tabata Timer by fit.how has these calculators built in, plus an interval timer you can read from across the gym. See the app.
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