Heart rate zones are the most-used training tool in amateur cycling, and also the most misunderstood. Nearly everyone has them set up on their head unit. Almost nobody has them set correctly, and even fewer use them the way they're meant to be used. Here's how they actually work — what each zone does, how to set yours from real data instead of a broken formula, and how to train with them so they make you faster instead of just decorating your ride file.
What heart rate zones actually are
Your heart rate is a window into how hard your body is working internally. As effort rises, your heart beats faster to deliver oxygen. Zones simply carve that range into bands, each corresponding to a different physiological gear — a different mix of energy systems and a different training adaptation.
Most systems use five zones. Here's what each one is for:
- Zone 1 — Active recovery. Very easy. The pace of a recovery spin or the warm-up and cool-down. It promotes blood flow and recovery without adding fatigue.
- Zone 2 — Endurance. Easy, all-day aerobic riding. This is the engine-building zone — where you develop the aerobic base, fat-burning efficiency and capillary density that everything else is built on. You can hold a conversation. Most of your training lives here, and it's the zone Iñigo San Millán's metabolic work put back on the map.
- Zone 3 — Tempo. Moderately hard. Feels productive, and has its uses, but it's the zone to be careful with — more on that below.
- Zone 4 — Threshold. Hard and sustained, right around the effort you could hold for roughly an hour. This is where you raise your functional threshold — the classic 2×20-minute interval lives here.
- Zone 5 — VO2max and above. Very hard, short intervals. Raises your aerobic ceiling — the roof that your threshold sits under.
Each zone earns its place. The skill isn't picking one zone; it's spending the right amount of time in each.
Setting your zones: throw out "220 minus age"
Here's where most riders go wrong before they even start. They set their zones from "220 minus age" — a formula that estimates your maximum heart rate — and build everything on top of it.
The problem: that formula is a population average, and real maximum heart rates vary enormously between individuals of the same age, often by 15-20 beats per minute or more. I've seen 45-year-olds with a genuine max of 195 and others at 165. Build your zones on a max that's 15 beats wrong and every single zone is wrong. You'll ride your "easy" zone too hard and your "threshold" zone in the wrong place.
The fix is to anchor your zones on your threshold heart rate, measured from an actual test — and threshold, not max, is the number that matters for training anyway.
The simplest field test: warm up well, then ride an all-out, evenly paced effort. A 20-minute test works — take your average heart rate over the effort as a close approximation of threshold (some use a 30-minute time trial and average the final 20 minutes, which is slightly more accurate because heart rate takes a few minutes to climb). That threshold heart rate becomes the anchor, and you set your zones as percentages of it. Your training app or coach can generate the bands from that one number.
Do the test properly, well-rested, and redo it a couple of times a year as your fitness changes. There's a fuller comparison of setting zones by heart rate, power and feel in zone 2 by heart rate vs power vs RPE.
The mistake that quietly ruins most riders' training
Once your zones are set correctly, the way you use them matters more than the zones themselves. And here's the single most common, most costly error in amateur cycling: too much time in the middle.
The research on how the best endurance athletes actually train — Stephen Seiler's work on training-intensity distribution is the landmark here — keeps landing on the same pattern. Around 80% of training is easy, in Zones 1-2. Around 20% is really hard, in Zones 4-5. Very little sits in the Zone 3 middle.
Why avoid the middle? Because Zone 3 is a trap. It's hard enough to generate real fatigue and stop you recovering, but not hard enough to drive the top-end adaptations that raise your ceiling. Live there and you get the fatigue cost of hard training with the adaptation of moderate training — the worst of both. It feels productive, which is exactly why so many amateurs do it and then plateau, baffled.
Discipline is the whole game. On easy days, keep your heart rate honestly in Zone 1-2 even though it feels almost too gentle — that's correct, that's the point. On hard days, actually reach Zones 4-5. Stop making every ride a moderately-hard slog. This is why Seiler and coaches like him keep hammering the "go easy to go fast" message, and why we made the case in Prof. Seiler on low-heart-rate cycling.
Heart rate's limits — and when to trust power or feel instead
Heart rate is brilliant, but it isn't perfect, and knowing its blind spots keeps you from being misled.
- It lags. When you jump into a hard effort, your heart rate takes 30-60 seconds to catch up. For short intervals — 30-second or one-minute efforts — the interval's nearly over before your heart rate reflects it. For those, power is far better because it's instant.
- It drifts. Over a long ride, your heart rate creeps up at the same effort — "cardiac drift" — from heat, dehydration and fatigue. A rising heart rate late in a ride doesn't always mean you're working harder.
- It's twitchy. Caffeine, heat, poor sleep, stress and even a hot indoor room all shift your heart rate for the same effort. Indoor and outdoor zones can differ noticeably, which we covered in heart rate zones indoor vs outdoor.
So the smart approach uses more than one lens. Use heart rate to keep easy and endurance rides honestly easy — it's perfect for that. Use power for short, hard intervals where heart rate is too slow. And use RPE — your own rating of perceived effort — as the tie-breaker that tells you when heart rate is lying because you're tired or overheated. Three tools, each for its right job.
Put it to work
Here's the whole thing distilled:
- Set your zones from a real threshold-heart-rate test, not "220 minus age."
- Spend around 80% of your riding easy, in Zones 1-2.
- Make your hard sessions really hard, reaching Zones 4-5.
- Stay out of the Zone 3 middle on purpose.
- Use power for short intervals, heart rate for easy rides, and RPE to keep both honest.
Do that and heart rate zones stop being decoration and start being the steering wheel for your training.
If you want your zones set properly and a plan built around the right intensity distribution — instead of guessing whether you're riding too hard or too easy — that's the foundation of every plan inside the Not Done Yet community. It's $195 a month at skool.com/roadmancycling. Set the zones right, ride the easy days easy, and watch what happens when your hard days finally have something left to give.