Calculate your 5 heart rate training zones using max HR or Karvonen formula.
Heart rate zones are training intensity ranges expressed as percentages of your maximum heart rate, used to structure cardiovascular training. The Karvonen formula — based on heart rate reserve (HRR) rather than just max heart rate — gives more accurate zones for individual fitness levels by accounting for resting heart rate.
Training in the right zone produces specific adaptations: Zone 2 (60–70% HRR) builds aerobic base and fat oxidation; Zone 4 (80–90%) builds lactate threshold; Zone 5 (90–100%) builds VO2 max. Most recreational athletes spend too much time in the moderate "grey zone" (Zone 3) which produces middling adaptations in all areas.
HR_{target} = ((HR_{max} - HR_{rest}) \times \%) + HR_{rest}
Inputs: 30-year-old · Resting HR 60 bpm · Target Zone 2 (65% HRR)
It is a population average accurate to within ±10–12 bpm. About a third of adults have a true max heart rate more than 10 bpm different from the formula. For precise zones, perform a max HR field test once a year: after a full warm-up, run 3-minute uphill repeats at maximum effort, taking the peak HR reading.
Day-to-day variation of 3–8 bpm is normal. Elevations of 10+ bpm above baseline usually signal incomplete recovery from a hard workout, illness onset, poor sleep, or psychological stress. Tracking morning HR with a wearable is one of the best early warning indicators of overtraining.
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