Heart rate zones for running, explained

Strap on a heart rate monitor and your watch will happily slot every run into a colour coded zone. It feels scientific. The catch is that almost every consumer device builds those zones on a single shaky number, your estimated maximum heart rate, and then applies a one size formula on top of it. Get the foundation wrong and every zone above it is wrong too.

This article explains the common five zone model and what each zone actually trains, why the famous 220 minus age estimate is so unreliable, how heart rate reserve improves on a flat percentage, and why anchoring your zones to a real test beats any formula based on your birthday.

The five zone model and what each zone trains

Heart rate zones are simply bands of intensity, usually expressed as a percentage of maximum heart rate. The most common system splits effort into five zones, each loosely mapped to a different physiological demand.

The percentages above are conventions, not laws, and different brands draw the lines in slightly different places. The deeper point made by Mann, Lamberts and Lambert (2013) is that a fixed percentage of maximum heart rate does not place every runner at an equivalent physiological stress. Two people at the same percentage of maximum can sit on opposite sides of their lactate threshold. The zone label is the same; the biology is not. If you want the physiology behind the most important of these bands, we cover it in Zone 2 training for runners.

Why 220 minus age is a poor estimate of your max

Nearly every zone calculator starts with the same equation: maximum heart rate equals 220 minus your age. It is simple, memorable and almost wrong by design. Robergs and Landwehr (2002) traced the formula’s history and found it was never derived from a controlled study at all. It emerged from an informal plot of data from around eleven mixed sources in the 1970s, was never validated, and yet became textbook gospel. Their verdict was blunt: the equation has no scientific merit for prescribing exercise.

The average is only half the problem. The real trouble is the spread. The standard error around 220 minus age is roughly 10 to 12 beats per minute. Because real maximums scatter widely around the mean, the formula can miss an individual by 20 beats or more in either direction. A runner whose true maximum is 190 might be told it is 175. Every zone built on that 175 would then sit too low, pushing genuinely easy runs into a higher zone label and threshold work off the chart.

Better formulas: Tanaka and Gellish

If you must use a formula, use a better one. Tanaka, Monahan and Seals (2001) pooled data from a large meta analysis and field study and produced the most widely cited replacement: maximum heart rate equals 208 minus 0.7 times age. The difference matters most at the ends of the age range. The classic formula systematically underestimates the maximum of older adults; Tanaka’s flatter slope tracks the real decline far more closely.

Gellish and colleagues (2007) reached a strikingly similar conclusion from a different angle, following the same individuals over many years rather than comparing different people once. Their longitudinal model produced roughly 207 minus 0.7 times age, again with a gentler age slope than 220 minus age. When two independent methods converge on almost the same equation, it is a strong signal. The honest caveat is that even these improved formulas still carry a standard deviation of several beats. They are better starting points, not personal truths.

Heart rate reserve and the Karvonen method

There is a second flaw in the simple approach: a flat percentage of maximum ignores your resting heart rate entirely. Two runners with the same maximum but very different resting rates have very different aerobic engines, yet a plain percentage treats them identically.

The fix is heart rate reserve, the gap between your maximum and your resting heart rate. The Karvonen method sets a target as your resting heart rate plus a chosen percentage of that reserve. So 70 percent of reserve for a runner with a maximum of 190 and a resting rate of 50 is 50 plus 0.7 times 140, which is 148 beats per minute, noticeably higher than 70 percent of maximum, which would be 133. Because it folds in resting heart rate, the reserve method tends to land zone boundaries closer to true metabolic thresholds than a raw percentage of maximum does. It is not perfect, but for a formula it is a meaningful upgrade.

The better anchor: thresholds and a field test

The most reliable zones are not built from your age at all. They are anchored to physiological landmarks, namely your ventilatory or lactate thresholds, or at minimum to a measured maximum from a hard test. Mann, Lamberts and Lambert (2013) argue that threshold anchored intensities produce a more equivalent training stress across individuals than any percentage of maximum, precisely because they target the metabolic transitions that matter.

You do not need a laboratory to start. To find your real maximum, warm up thoroughly, then run several efforts of three minutes up a gentle hill, building the last one to all out, and note the highest heart rate your monitor records. Do it twice on separate fresh days and take the higher figure. To anchor the more useful threshold zones, a 20 to 30 minute time trial gives you an estimate of threshold heart rate that you can build zones around. That single test will beat 220 minus age every time. We go deeper into pacing those efforts in lactate threshold running.

Why bother getting the anchor right? Because the whole point of zones is to keep your easy running easy and your hard running hard. Seiler (2010) documented that elite endurance athletes spend roughly 80 percent of their sessions at genuinely low intensity, below the first lactate threshold. If your zones are miscalibrated, you cannot reliably stay there, which is exactly how so many runners drift into the moderate grey zone. We unpack that trap in why most runners train too fast.

The drift caveat: heat, fatigue and long runs

Even perfectly calibrated zones come with a warning label. Heart rate is not a fixed readout of effort; it drifts. Coyle and González-Alonso (2001) described cardiovascular drift, the gradual rise in heart rate during prolonged exercise even when pace and power stay constant. Stroke volume falls, so heart rate climbs to compensate.

This is why heart rate works best as one input among several. Pair it with pace, with the talk test, and with rating of perceived exertion, and the occasional drifting number stops being a problem. The zones tell you the plan; your breathing tells you the truth.

Frequently asked questions

Related reading: Zone 2 training for runners: what the research actually shows.