Key takeaways
- Use heart-rate reserve (max minus resting), not percent of max; the error is often a whole zone.
- Get max from a real maximal effort, resting from overnight wearable data.
- Validate with the talk test: full sentences in zone 2, phrases in zone 3, words in zone 4.
The 220-minus-age formula is wrong for most individuals by ten beats or more, and percent-of-max zones built on it are wrong by more. There is a better way that needs nothing but a watch.
Two numbers
Resting heart rate: take the lowest overnight reading your wearable reports across a normal week. Maximum heart rate: the highest reading from a genuinely maximal effort in the past year, such as the last minute of a hard 5K or the top of a long hill sprint. If you have neither, 208 minus 0.7 times your age is a better starting formula than 220 minus age.
The Karvonen formula
Heart-rate reserve is max minus resting. Each zone boundary is resting plus a percentage of reserve. Worked example: max 188, resting 52, reserve 136.
- Zone 1, recovery: under 60% → below 134
- Zone 2, aerobic base: 60 to 75% → 134 to 154
- Zone 3, tempo: 75 to 87% → 154 to 170
- Zone 4, threshold: 87 to 95% → 170 to 181
- Zone 5, max: above 95% → above 181
Compare with percent-of-max: 75% of 188 is 141, which would put this runner's whole zone 2 into zone 1. That is the size of the error.
Checking it against feel
Zone 2 should allow full sentences. Zone 3 allows short phrases. Zone 4 allows a word or two. If your calculated zone 2 does not match the talk test, your max is probably wrong; fix the max, not the formula.
Zones that move with you
PeakBeat computes zones by Karvonen from your watch's resting rate and your recorded max, updates them as those change, and uses them to choose music. Your bands, your thresholds, and a track that fits where your heart is right now.
PeakBeat is built for this
Your effort writes the setlist. Coming soon, free during the beta.
Questions
What if my watch's max heart rate looks too high?
Do zones change with fitness?
Are five zones necessary?
Sources
- Karvonen M.J., Kentala E., Mustala O. (1957). The effects of training on heart rate: a longitudinal study. Ann Med Exp Biol Fenn. https://pubmed.ncbi.nlm.nih.gov/13470504/