Load & readiness

Heart rate zones

Five effort bands, set from the room between your resting and maximum heart rate.

Coaching heuristic

The %HRR method (Karvonen) and the Tanaka maximum are peer-reviewed; the specific five-zone cut-points are a widely-used convention, not a physiological boundary.

Heart rate zones split your effort into five bands so you can see at a glance whether you trained easy or hard. We use the Karvonen heart-rate-reserve method, which personalises the bands to your own resting and maximum heart rate rather than to a generic table.

The idea in one line

Your heart-rate reserve is the room between resting and maximum. We express any heart rate as a percentage of that reserve (%HRR), then read off which band it lands in.

%HRR = (HR − HR_rest) ÷ (HR_max − HR_rest)

This reserve-based method is peer-reviewed (Karvonen, 1957). A heart rate is placed in a zone purely by its %HRR, so the same beat count means a genuinely easier effort for a fitter heart with a lower resting rate.

The five zones

Each zone starts at a fixed fraction of your reserve. These cut-points (50%, 60%, 70%, 80%, 90%) are a widely-used convention, not a measured physiological boundary. They are a useful shared vocabulary, not a line your body actually draws.

Zone 1 Recovery: from 50% of reserve
Zone 2 Easy: from 60% of reserve
Zone 3 Aerobic: from 70% of reserve
Zone 4 Threshold: from 80% of reserve
Zone 5 Max: from 90% of reserve and above

From a percentage to a heart rate

To turn a %HRR bound into a target in beats per minute, we run the reserve maths in reverse:

bpm = HR_rest + fraction × (HR_max − HR_rest)

The five zones as bpm bands for an athlete with a resting HR of 50 and a max of 190. Anything under 120 bpm sits below Zone 1.

Finding your maximum

Every zone hangs off your maximum heart rate, so we take it seriously. We learn it from the highest heart rate you have actually recorded. If we have none yet, we fall back to Tanaka's formula:

HR_max = 208 − 0.7 × age

Tanaka (2001) is a meta-analysis of more than 18,000 people and is more accurate across the age range than the older 220 minus age rule. Even so, any age-predicted max carries a standard deviation of about 10 bpm (roughly a 20 bpm span across a 95% range), so a heart rate you have genuinely hit always wins over a formula.

Worked example

Our athlete has a resting HR of 50 and a max of 190, so a reserve of 140 bpm. Take a reading of 150 bpm:

Reserve used: (150 − 50) ÷ (190 − 50) = 100 ÷ 140 = 0.714 = 71%
71% lands in Zone 3 (Aerobic, 70-80%).

Going the other way, Zone 2 (Easy) runs from 60% to 70% of reserve:

Lower bound: 50 + 0.60 × 140 = 134 bpm
Upper bound: 50 + 0.70 × 140 = 148 bpm

So for this athlete, an easy run means holding roughly 134-148 bpm.

What it is and is not

Treat zones as a guide, not a precise dial. The boundaries are conventional, and heart rate lags the effort that drives it and is pushed around by heat, caffeine, and fatigue, so the same pace can read a zone higher on a hot afternoon than on a cool morning. The %HRR method (Karvonen) and the Tanaka maximum are both peer-reviewed. The specific five-zone cut-points are a convention layered on top, useful for talking about effort but not a physiological law.