Why the 220 minus age formula fails
Maximum heart rate estimated from age can be off by 10-12 beats. Why that happens and what to use instead.
It's the most famous formula in sport: maximum heart rate equals 220 minus your age. Easy to remember, but a poor basis for training.
The error problem
The formula comes from population averages. For an individual, the typical error is around 10-12 beats either way. For a 40-year-old runner the formula says 180, but their real maximum could be 165 or 195.
What happens to your zones
If your zones come from a poorly estimated maximum, they all shift. You could be doing your "easy" runs in the tempo zone without knowing it, or your intervals too soft.
What to do instead
- Use threshold: zones based on threshold heart rate are more reliable than those based on maximum.
- Look at your data: the highest heart rate you've seen in a race or hard intervals is a better estimate than any formula.
- Review: maximum heart rate changes little with training, but threshold does.
If you have no data yet, the formula will do to get started. But as soon as you have a few weeks of workouts, replace it with real values.