Understanding Heart Rate Training Zones
Zone 1 – Fat Burn (50–60% MHR): Easy effort, sustainable for hours. Burns highest fat percentage but lowest total calories. Good for warm-ups, recovery, and beginners. Zone 2 – Cardio (60–70% MHR): Moderate effort, improves cardiovascular health. AHA recommends 150 min/week in this zone. Zone 3 – Aerobic (70–80% MHR): Improves aerobic capacity and endurance. Zone 4 – Threshold (80–90% MHR): Hard effort, improves lactate threshold and speed. Zone 5 – Max (90–100% MHR): All-out effort, only sustainable for seconds to 2 minutes. Source: ACSM 2023; AHA 2023.
Tanaka MHR = 208 − (0.7 × 35) = 183.5 bpm
Karvonen Fat Burn (50–60%): ((183.5−65) × 0.50)+65 = 124–136 bpm
Cardio Zone (60–70%): 136–148 bpm
Karvonen vs Percentage of MHR
The Karvonen (Heart Rate Reserve) method is more accurate because it accounts for individual resting heart rate. A fit person with a low resting HR has a higher heart rate reserve and can work at higher intensities within the same percentage zones. For general purposes, simple percentage of MHR is sufficient. Source: Karvonen MJ et al. 1957.
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