Training Zones, Explained: Heart Rate, FTP and Pace From One Threshold

Two athletes both “did an easy ride,” but one trained at 60% of threshold and the other at 80%, and over a season those two definitions of “easy” produce completely different fitness. Training zones exist to replace vague effort labels with numbers, and the surprising thing is how little you need to generate them: one good threshold value — your FTP, your lactate-threshold heart rate, or your threshold pace — anchors an entire ladder of zones. Get that one anchor right and every zone falls into place.

Everything hangs off threshold

A threshold is the intensity you can sustain for roughly an hour all-out before fatigue runs away from you. It’s the natural pivot for zones because it sits at the edge of your sustainable aerobic effort: below it you can go long, above it the clock starts ticking fast. Rather than measure VO₂ max in a lab, modern zone models express every zone as a percentage of threshold, so the whole system scales to you personally and updates the moment your threshold improves.

Three thresholds, depending on what you measure: FTP (functional threshold power, in watts) for cycling, LTHR (lactate threshold heart rate, in bpm) for heart-rate training, and threshold pace (your roughly one-hour race pace) for running. Each anchors its own model.

Coggan power zones for cycling

For cyclists training with a power meter, the Coggan 7-zone model is the standard, expressed as a percentage of FTP:

Z1 Active Recovery   ≤ 55%    easy spinning
Z2 Endurance         56–75%   long aerobic base
Z3 Tempo             76–90%   sustained efforts
Z4 Threshold         91–105%  right around FTP
Z5 VO₂ Max           106–120% 3–8 min intervals
Z6 Anaerobic         121–150% 30s–3 min efforts
Z7 Neuromuscular     > 150%   sprints

Notice Z4 straddles 100% — your threshold sits inside the threshold zone, not at its top. Power is the most precise anchor because watts are watts regardless of heat, fatigue or hills, which is why power zones don’t drift the way heart rate does.

Friel heart-rate zones

Heart rate is the most accessible signal — every chest strap and watch reports it — and the Joe Friel model anchors HR zones to LTHR rather than to maximum heart rate. That’s deliberate: threshold heart rate is a far more individual, trainable marker than the crude 220 − age estimate of max HR. Friel’s zones run from recovery up through a split Z5 (5a/5b/5c) covering threshold, VO₂ aerobic capacity and anaerobic capacity, with the key transitions clustered tightly just below and above 100% of LTHR.

If you only know your maximum heart rate, a common shortcut is to estimate LTHR as about 85% of HRmax, then build the zones from there. It’s an approximation — a proper threshold test is better — but it gets you usable zones today. Remember that heart rate lags effort and drifts upward in heat and dehydration, so a Z2 ride can creep into Z3 heart rates on a hot day even at the same power.

McMillan-style pace zones for runners

Runners can anchor on threshold pace and derive training paces as ratios of it. Because faster running means a smaller time per kilometre, the multipliers invert relative to power: easy paces are a larger number (slower) than threshold, and interval paces are a smaller number (faster):

Easy        1.30–1.50 × threshold pace   recovery & base
Long run    1.15–1.30 ×                   aerobic endurance
Marathon    1.03–1.08 ×                   marathon effort
Tempo       0.97–1.03 ×                   threshold
Interval    0.91–0.96 ×                   VO₂ max
Speed       0.85–0.90 ×                   5K and faster

The big takeaway most runners need: easy days should be properly easy — 30 to 50% slower than threshold pace — which almost always feels too slow until you see the fitness gains from not turning every run into a tempo run.

Why the three signals disagree — and which to trust

A common confusion is finding yourself “in Z2 by power but Z3 by heart rate” on the same ride. That’s not a calibration error; it reflects what each signal measures. Power is an input — the work you produce right now — so it responds instantly and doesn’t care about the weather. Heart rate is an output — your body’s response to that work — so it lags by a minute or two, drifts upward over a long effort (a phenomenon called cardiac drift), and climbs in heat, at altitude or when you’re under-recovered. Pace sits in between: honest on a flat road, but distorted by hills, wind and soft trails.

The practical rule is to anchor on the most direct signal you can measure. Cyclists with a power meter should let power lead and treat heart rate as a secondary fatigue gauge. Runners on flat ground can trust pace, but on hilly or technical terrain should switch to heart rate or effort. And everyone benefits from re-testing threshold every four to six weeks of consistent training — as fitness improves, yesterday’s Z2 becomes today’s recovery pace, and stale zones quietly send you training too easy.

The 80/20 reason zones matter

The whole point of computing zones is to control how much time you spend where. Endurance research keeps landing on polarised training: roughly 80% of training volume easy (Z1–Z2) and only about 20% hard (Z4 and above), with surprisingly little in the tempo middle. Most amateurs do the opposite — too many medium-hard days that are too tiring to be easy and too easy to drive adaptation. Zones turn that abstract advice into a checkable plan: if your easy runs keep showing up in Z3, your zones are telling you to back off.

Generate your zones

You don’t have to do this arithmetic by hand. The Heart Rate, FTP & Pace Training Zone Calculator takes a single anchor — your FTP in watts, your LTHR or HRmax in bpm, or your threshold pace — and generates the full zone ladder using the Coggan power model, Friel HR model, or McMillan-style pace ranges, so the same tool serves cyclists, heart-rate trainers and runners. From there, the Running Pace Converter helps you translate those pace zones across distances and units, and the Cycling Power-to-Speed Calculator shows what your power zones actually mean on the road. Find your threshold once, build your zones from it, and “easy” and “hard” stop being guesses.