Find your five training heart rate zones for fat burn, aerobic base, threshold, and peak performance using the Karvonen formula.
The Karvonen formula accounts for your resting heart rate when calculating training zones, making it more personalized than simple percentage-of-max-HR methods. It calculates your Heart Rate Reserve (HRR = Max HR − Resting HR) and applies percentages to that range.
Zone 2 (aerobic base) is where fat oxidation is highest and where most endurance athletes spend 80% of their training time. It feels conversational — you can speak in full sentences. Consistent Zone 2 training builds your aerobic engine, improves mitochondrial density, and is the foundation of long-term cardiovascular health.