Cycling training zones: FTP or heart rate

With cycling training zones you know before you clip in whether a ride should stay easy or go hard, and once you're riding you can hold that intensity instead of guessing. The zones hang on one of two numbers: your functional threshold power (FTP) or your heart rate. That choice decides how precise the zones are and what you need to set them up.

What your FTP tells you

FTP is the power you can hold for about an hour. Few riders want to go all out for a full hour, so the usual shortcut is a 20-minute FTP test: ride as hard as you can sustain, take your average power and multiply it by 0.95. The other common format is a ramp test, where the load climbs in steps until you can't keep up, and FTP is estimated from how far you got.

On average, the 20-minute value holds up well. In 23 trained cyclists, FTP from the 20-minute test matched both the power they held for 60 minutes and their individual anaerobic threshold, and the values were closely related (Borszcz 2018). The spread between riders was large, though. For you as an individual, the 20-minute and the 60-minute numbers can differ noticeably, and the authors advise against treating them as interchangeable (Borszcz 2018).

Training status shifts the picture too. In a group of 20 cyclists, FTP and lactate threshold were strongly related (r = 0.95). In trained riders the two matched, while in recreational riders FTP sat clearly below the lactate threshold (Valenzuela 2018). A review of 25 threshold concepts treats the maximal lactate steady state as the reference (Faude 2009). FTP is a practical field value that comes close to it, and for less trained riders it tends to land a little low.

Power zones need hardware: a power meter on the bike or a smart trainer that measures watts.

Heart rate needs less gear and more care

A chest strap is all it takes. Heart rate zones are usually set as percentages of your maximal heart rate, and the quickest way to that number is an age formula. The formula scatters widely. For any one rider, the estimate can be off by about ten beats either way (Achten 2003). Zones built on a threshold heart rate from a test do better: fixed percentages of maximal heart rate separate the intensity domains poorly, while thresholds measured in a test separate them more cleanly (Jamnick 2020).

Then there's the way heart rate behaves on the bike. It follows a change in workload with a delay, which makes it of little use for short intervals, because by the time it catches up the effort may be over (Achten 2003). On long rides it drifts upward while your power stays the same, above all in heat and when you lose fluid (Coyle 2001). And at the same workload it varies from day to day with form, heat, hydration, altitude and fatigue (Achten 2003).

So read a heart rate zone as a range with some slack in it. A number from this morning's ride and the same number next week don't always mean the same effort.

Which measure fits which ride

Watts work best when the structure is tight, such as intervals and threshold blocks on an indoor trainer. Power shows the load as you produce it, so you can settle into a target within a few pedal strokes and stay there.

Heart rate does its best work on long, easy rides, where the lag doesn't matter and a ceiling keeps the ride from creeping harder. It's also a good second measure next to power. Ride a familiar session and compare. If your heart rate sits where it always does but the watts come in lower, that's often fatigue showing. That reading is coaching practice, not a study result.

When neither number is available, or the day has turned out differently from the plan, perceived effort is the fallback. RPE is a scale you rate yourself, usually from 1 to 10. In coaching practice, riders who check it after every session get surprisingly good at it, and it works on any bike, in any weather.

If you train for more than one sport, the same logic applies on foot. The running counterpart is how to find your threshold pace for intervals.

The zones you'll use most

Whether your cycling training zones run on watts or heart rate, the model comes with five or seven zones. They share one idea: intensity rises in steps from easy to maximal, with the threshold as the anchor. For planning, a handful of them carry most of the weight.

Most of your riding belongs in the easy zone. Well-trained endurance athletes split their sessions roughly 80 to 20, about 80 percent easy and about 20 percent hard (Seiler 2010). Easy should feel easy, and on long rides a heart rate ceiling helps you keep it that way.

The threshold zone sits around your FTP. It's the zone for sustained hard blocks of several minutes or more, and it's where an accurate FTP matters most.

Above it sits the zone for short, hard intervals. Heart rate can't keep up here (Achten 2003), so watts or perceived effort guide the effort.

If you also lift, your hard days have to share the week with strength sessions, and a cycling training plan has to leave room for them. How strength and endurance fit into one plan is the subject of our guide to hybrid training.

When to retest your FTP

Your FTP changes as you train, so the zones built on it need a fresh test from time to time. In coaching practice, four moments call for one.

The first is the end of a training block, when the work of the past weeks should show up in the number. The second is when your intervals start to feel easier than they should at the prescribed watts, a sign the zones have fallen behind you. After a break, test again before you trust the old value, because a number set too high makes every structured session a struggle. And if you switch between indoors and outdoors, expect a difference. In our experience indoor values often come out a little lower, so test where you'll do most of your structured work.

If you plan your cycling with Tahto, you update the FTP yourself after a new test. The help text explains the ramp test and the 20-minute test, but the app never schedules a test as a session. Between tests, your plan keeps power targets within what your logged rides show and backs them off when two rides in a row come in well below target.