How do I find my maximum heart rate?

From a real maximal effort rather than a formula. The highest reading from a hard 5K race, or from a session of hard hill repeats, is usually within a beat or two. Formulas can be 20 beats out for an individual.

What zone should easy runs be in?

Zone 2, roughly 60 to 75 percent of maximum. If you are consistently drifting into zone 3 on easy runs, you are running them too fast.

Why is my heart rate higher than usual today?

Heat, dehydration, poor sleep, illness, caffeine or stress. All of them raise heart rate at a given pace. A day where it is 8 to 10 beats up at your normal easy pace is a reasonable day to make the session easier.

Should I train by heart rate or pace?

Pace for hard sessions, where you want a specific intensity and heart rate lags. Heart rate for easy runs, where it stops you running too fast, and on hot days when pace no longer reflects effort.

Guide

Heart rate zones for runners

Heart rate is a useful training signal and a bad master. Most runners set their zones with a formula that is wrong for them, then trust the numbers in exactly the conditions where they are least reliable.

The five zones

Percentages of maximum heart rate. Zone boundaries vary between systems; these are the common running convention.

Zone	Percent of max HR	Feels like	Used for
1 Recovery	50 to 60	Very easy, almost walking effort	Recovery runs, warm-ups
2 Easy	60 to 75	Conversational, sustainable for hours	The bulk of your weekly volume
3 Steady	75 to 85	Comfortable but not chatty	The grey zone. Use sparingly
4 Threshold	85 to 92	Comfortably hard, about an hour max	Tempo and threshold sessions
5 VO2max	92 to 100	Hard. Minutes, not hours	Intervals

Why 220 minus age is a bad method

The formula was never intended as a training tool. It came from a rough fit through a scatter of population data, and the standard deviation around it is roughly 10 to 12 beats per minute. For an individual runner it can easily be 20 beats out.

Twenty beats of error moves every zone boundary. A runner whose true max is 195 but who trains off a calculated 180 will run their easy runs 15 beats too slow, which is annoying, or their threshold sessions 15 beats too hard, which is worse.

It is a particularly poor fit for masters runners, where individual variation grows.

Better ways to set your zones

Measured maximum. The highest heart rate you have actually seen in a hard race or a maximal effort. A hard 5K or a set of hill repeats to exhaustion will get you close. Use the peak from a real effort, not a formula.
Threshold heart rate. Better than max for most training purposes. Run a hard 30 minute time trial alone; your average heart rate over the last 20 minutes is a good estimate of threshold. Set zones as percentages of that.
Heart rate reserve. Uses both max and resting heart rate, which accounts for individual differences better than max alone. Zone percentage of (max minus resting), plus resting.
Just use pace. For most runners on most days, paces derived from a recent race are more actionable than heart rate and do not drift with heat, sleep or caffeine.

Cardiac drift is a signal worth reading

On a long run at constant pace, heart rate typically rises over time as plasma volume drops and core temperature climbs. Five to ten beats over an hour is normal.

The useful part is that the size of that drift tracks aerobic fitness. As you get fitter, the same pace produces less drift. Comparing drift across similar runs over a block is one of the better home measures of whether the base is actually building, and it is more informative than any single day's heart rate reading.

Frequently asked

How do I find my maximum heart rate?: From a real maximal effort rather than a formula. The highest reading from a hard 5K race, or from a session of hard hill repeats, is usually within a beat or two. Formulas can be 20 beats out for an individual.
What zone should easy runs be in?: Zone 2, roughly 60 to 75 percent of maximum. If you are consistently drifting into zone 3 on easy runs, you are running them too fast.
Why is my heart rate higher than usual today?: Heat, dehydration, poor sleep, illness, caffeine or stress. All of them raise heart rate at a given pace. A day where it is 8 to 10 beats up at your normal easy pace is a reasonable day to make the session easier.
Should I train by heart rate or pace?: Pace for hard sessions, where you want a specific intensity and heart rate lags. Heart rate for easy runs, where it stops you running too fast, and on hot days when pace no longer reflects effort.

Stop reading. Start training.

This is the theory. Shed is the schedule.

Knowing what a threshold run is for does not tell you which Tuesday to run one, or how fast, or what to do when you miss it. Shed writes every session of your race block and adjusts it as you train. Ask it where a number came from and it will tell you.

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