Heart Rate Zones Explained: The 5-Zone Model for Runners and Cyclists

Heart-rate zones are simple in theory and ruthlessly easy to set up wrong. The default chart shipped with most watches uses '220 minus age' — a formula with a standard error of ±10–12 bpm. For a 40-year-old, that means your real max could be 168 or 192. Training prescriptions built on that number are guesses dressed up as science.

Anchor zones to your threshold, not your max

The cleanest method: find your lactate threshold heart rate (LTHR), which corresponds to the upper edge of comfortably-hard sustainable effort — roughly the pace you could race for an hour. Every other zone calculates from there. LTHR is far easier to measure than HRmax and far more stable across training cycles.

How to find your LTHR

1. 01Warm up 15 minutes, then run a hard 30-minute time-trial — solo, flat, after a recovery day
2. 02Press lap 10 minutes in, then hold steady to the finish
3. 03Your average HR for those final 20 minutes ≈ your LTHR

The 5-zone model (Joe Friel / Coggan-style)

• Zone 1 — < 85% LTHR — active recovery, warm-up, cool-down
• Zone 2 — 85–89% LTHR — aerobic base, long-run pace, the bread and butter
• Zone 3 — 90–94% LTHR — 'no man's land' tempo, useful in moderation
• Zone 4 — 95–99% LTHR — threshold work, race pace 10K–half marathon
• Zone 5 — 100%+ LTHR — VO2max intervals, true top-end work

The polarized rule

Decades of training research, from Stephen Seiler onward, point to the same shape: 80% of your weekly training time in Z1–Z2, and 20% in Z4–Z5. The dangerous middle — Z3 — should be the smallest slice, not the biggest. Most amateurs invert this distribution and wonder why they plateau.

Running vs cycling heart rate

LTHR is sport-specific. Cycling LTHR is typically 5–10 bpm lower than running LTHR because cycling recruits less muscle mass. Set zones separately for each sport. Don't paste your running zones onto the bike — your Z2 ride will end up in Z3 territory.

Heart rate drift and what it tells you

On a steady aerobic run, HR will drift up over time even as pace stays constant — that's normal cardiac drift from heat and fluid loss. The size of the drift matters. Under 5% drift over a long run means strong aerobic fitness. Over 10% means you're either underfueling, undertrained, or going too hard.

Heart rate is the truth-teller of endurance training. Pace tells you what you did; heart rate tells you what it cost.

Common HR training mistakes

• Relying on the watch's auto-calculated max (it's almost always wrong)
• Running Z2 as a number target instead of a perceived effort — chase 'conversational,' verify with HR
• Ignoring sleep, stress, caffeine, and heat — all bias HR ±5–10 bpm
• Skipping the 30-minute time trial because it hurts (it does; do it anyway)