About the heart rate zones calculation
Heart rate zones turn "go hard" or "go easy" into numbers you can actually train against. The Karvonen method uses heart-rate reserve — the gap between resting and maximum — which personalises the zones far better than a flat percentage of max.
Formula
Max HR = 208 − (0.7 × age) [Tanaka, 2001]
HR reserve = max HR − resting HR
Zone bound = (HR reserve × intensity) + resting HRWorked example
A 25-year-old with a resting HR of 60: max = 208 − 17.5 = 190.5, reserve = 130.5. Zone 2 (60-70%) runs from (130.5×0.6)+60 = 138 to (130.5×0.7)+60 = 151 bpm.
Frequently asked questions
Why not 220 − age?
It was never derived from proper research and carries a standard deviation of around 12 bpm. Tanaka et al. validated 208 − 0.7×age across a much wider age range, and it is meaningfully more accurate at both ends.
What is zone 2 training?
Zone 2 is roughly 60-70% of heart-rate reserve — comfortable enough to hold a conversation. It builds aerobic base and mitochondrial density, and it is where most endurance athletes spend the large majority of their training time.
How do I find my true resting heart rate?
Measure immediately on waking, before sitting up, across several consecutive mornings and take the average. A wearable that records overnight will do this for you. Typical adults sit between 60 and 100 bpm; trained endurance athletes are often in the 40s.
Sources
- Tanaka H, Monahan KD, Seals DR — Age-predicted maximal heart rate revisited (2001)
- Karvonen MJ, et al. — The effects of training on heart rate (1957)