Heart-rate training zones for runners

Finding maximum heart rate

Age formulas (220 − age, or 208 − 0.7 × age) are rough. Individual variation of ±10–15 bpm is common — enough to misplace an entire zone.

Better: an all-out effort with a chest strap (not wrist optical) — a steep hill sprint or a hard 1K. Lab lactate or spiroergometry remains the gold standard when you can access it.

Many modern watches estimate max HR from a few hard sessions. Treat those as drafts until confirmed by a true maximal effort.

What each zone trains

GA0 (<70%) — active recovery. Little fitness gain; keeps blood flowing after hard days.

GA1 (70–80%) — the bulk of endurance volume. Builds mitochondria and capillarisation so you can absorb more training later.

GA2 (80–85%) — steady aerobic work. Still clears lactate as fast as you produce it; useful bridge between easy and threshold.

GA3 (85–90%) — marathon-relevant effort near or just below threshold. Tempos and long-run finishers live here.

WSA (>90%) — race-specific and interval work. Time here is limited; quality beats junk intensity.

Why Karvonen can feel fairer

Percent of max ignores resting heart rate. Two athletes with max 190 but resting 45 vs 65 have very different reserves. Karvonen uses HRR = max − rest, then targets % of that reserve added to rest.

Enable Karvonen in the tool when you know a reliable morning resting HR. It often places easy runs slightly higher in absolute bpm for low-rest athletes — closer to how those runners actually feel.

Race-day heart rates

Marathon effort typically sits around 85–90% of max; half marathon near 88–92%; 10K around 90–94%; 5K 92–95%. These are population averages — heat, hills and nerves push numbers up.

If race HR is high but pace is slow, look at fueling, heat and aerobic base before blaming “fitness”. Pair zones with pace from a recent race VO2 estimate for a fuller picture.