Power meters have completely changed cycling. What used to be reserved for professional teams is now bolted to thousands of bikes at Saturday morning bunch rides and midweek solo sessions. The technology itself is brilliant — real-time, objective measurement of exactly how hard you're working. But here's the uncomfortable truth: most riders who own a power meter aren't getting much from it. They watch the number bounce around on their head unit, maybe chase a higher average, and call it a day. Without a framework for understanding what those numbers mean, a power meter is just an expensive speedometer for your legs.
That framework is power zones. They take the raw wattage and give it context — turning an abstract number into a training language you can use every single ride. Instead of "I rode hard today," you get "I spent 40 minutes at threshold and 15 minutes in VO2max." That distinction is the difference between guessing and actually training.
What are power zones?
Power zones are intensity ranges calculated from your Functional Threshold Power (FTP) — the maximum power you can sustain for roughly one hour. Your FTP is the anchor point, and everything else is expressed as a percentage of it. If your FTP is 250 watts, then riding at 188 watts puts you squarely in the endurance zone. Riding at 263 watts means you're at threshold. The numbers are personal to you, which is why two riders sitting side by side in a bunch can be in completely different zones despite holding the same speed.
Think of zones like gears for your physiology. Each one targets a different energy system, creates a different training stimulus, and feels distinctly different in your legs and lungs. Zone 2 builds your aerobic engine over months. Zone 5 pushes your VO2max ceiling in sharp, painful intervals. You wouldn't use a hammer to tighten a screw, and you wouldn't ride zone 5 efforts to build your base. Zones give every session a purpose, and that purpose compounds over weeks and months into genuine fitness.
The most widely used model is Dr Andrew Coggan's seven-zone system. It's been the standard in cycling coaching for over a decade, and it's what most training platforms — including Veloi — use as a foundation.
The seven zones explained
Here's what each zone means in practice, not just in theory. For the examples below, we'll use a rider with an FTP of 250 watts to keep the numbers concrete.
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Zone 1: Active Recovery (below 55% FTP / under 138w) — This is genuinely easy. Easier than most people think. You should be able to hold a full conversation without any effort. Your breathing is barely elevated. It feels like you're not really doing anything — and that's the point. Zone 1 promotes blood flow and recovery without adding training stress. Use it on recovery rides the day after a hard session, or as the easy spin between intervals. The mistake most riders make is riding "easy" at 65-70% FTP, which is not recovery — it's just moderate fatigue with none of the adaptation benefits of harder work.
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Zone 2: Endurance (56-75% FTP / 140-188w) — The workhorse zone. You can talk in full sentences but you know you're working. This is where your aerobic base lives — the mitochondrial density, fat oxidation efficiency, and cardiovascular adaptations that underpin everything else. Long rides in zone 2 are the bread and butter of any serious training plan. A typical session might be two to four hours at a steady 60-70% FTP. It's not glamorous, but riders who build a deep zone 2 base see benefits at every intensity above it.
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Zone 3: Tempo (76-90% FTP / 190-225w) — Conversation becomes choppy. You can get a sentence out but you'd rather not. Tempo is a useful zone for time-crunched riders who can't do four-hour endurance rides — 90 minutes of solid tempo delivers a meaningful aerobic stimulus. But it's also the zone where many riders accidentally live, which causes problems we'll get to later. A tempo session might be 2x20 minutes at 82-85% FTP with five minutes of recovery between efforts.
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Zone 4: Threshold (91-105% FTP / 228-263w) — This is the business end. Threshold work is hard — your breathing is heavy, your legs are loading up with lactate, and you're counting down the minutes. But it's also where substantial fitness gains happen. Training at threshold raises your FTP, which lifts all your zones. Classic sessions include 2x20 minutes at FTP, or 3x15 minutes at 95-100% FTP. The key is accumulating time in this zone without going over the edge into zone 5, where you'll blow up and cut the session short.
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Zone 5: VO2max (106-120% FTP / 265-300w) — Now you're breathing hard enough that talking is out of the question. VO2max intervals push the upper limit of your aerobic system — how much oxygen your body can process. These are typically three to eight minutes long with equal or longer recovery between them. Think 5x4 minutes at 110% FTP with four minutes of easy spinning between sets. It hurts, but the ceiling you raise here gives you room to grow everywhere else. Riders who avoid zone 5 eventually plateau.
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Zone 6: Anaerobic Capacity (121-150% FTP / 303-375w) — Short, sharp, and savage. Efforts of 30 seconds to two minutes that push well beyond what your aerobic system can sustain. You're drawing heavily on anaerobic energy here — it's the kind of effort you make to close a gap in a race, crest a steep kicker, or win a town sign sprint. Training in zone 6 improves your ability to tolerate and repeat these surges. A typical session might be 8x1 minute at 130% FTP with two minutes of rest.
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Zone 7: Neuromuscular Power (maximal sprints) — There's no percentage range here because zone 7 is simply everything you've got. These are all-out sprints of five to fifteen seconds — pure neuromuscular power. Think standing starts, max sprints, and short explosive efforts. They train your ability to recruit muscle fibres rapidly and produce peak power. Even if you never race, a few zone 7 sprints in your training develop a kind of top-end snap that makes everything below feel more comfortable.
Finding your FTP
Your zones are only as accurate as the FTP they're based on. The classic test is the 20-minute effort: after a thorough warm-up, you ride as hard as you can sustain for 20 minutes, then multiply your average power by 0.95. That correction factor accounts for the fact that most people can hold slightly more power for 20 minutes than they can for a full hour. So if you average 280 watts for 20 minutes, your estimated FTP is 266 watts.
There are other approaches. Ramp tests start easy and increase the resistance every minute until you can't hold on — they're shorter and arguably less mentally gruelling, though some coaches debate their accuracy. Eight-minute tests use two efforts with the correction factor adjusted accordingly. Each protocol has trade-offs, and honestly, the test you'll actually do consistently is the best one.
But here's what experienced coaches know: a single test on a single day is just a snapshot. Your FTP shifts with fatigue, motivation, fuelling, and even the weather. A better approach is to let your data tell the story over time. If you're regularly doing 20-minute efforts at 270 watts in training, your FTP is probably around 257 — no formal test required. Your best efforts across various durations paint a power profile that's more accurate than any single test. This is exactly the kind of pattern recognition that an AI cycling coach excels at — continuously monitoring your power data and flagging when your FTP has likely shifted.
Don't overthink the test itself. An FTP that's five watts off in either direction won't ruin your training. What matters is having a reasonable starting point and updating it as your fitness changes.
The zone 2 debate
If you've spent any time in cycling forums or listening to training podcasts, you've heard the zone 2 hype. Polarised training, base miles, "go slow to go fast" — it's everywhere, and for good reason. The science is compelling: long, steady efforts in zone 2 drive mitochondrial adaptations, improve fat metabolism, strengthen your heart's stroke volume, and build the aerobic foundation that supports every other kind of effort you do on the bike.
The debate isn't really about whether zone 2 is important — virtually every coach agrees it is. The argument is about how much is enough and how easy "easy" really needs to be. Research on elite endurance athletes consistently shows they spend 75-80% of their training time at low intensity. For amateur cyclists with ten hours a week, that ratio might shift slightly, but the principle holds: most of your riding should feel uncomfortably easy.
The problem is that most riders don't actually ride zone 2 when they think they are. They head out for an "easy ride," start feeling good after twenty minutes, push the pace on a climb, respond to a Strava segment, and suddenly their average power is 80% of FTP — which is tempo, not endurance. This drift into what coaches call "no man's land" is one of the most common training mistakes in cycling, and it's worth its own section.
Common mistakes with power zones
Living in zone 3. The single most prevalent mistake. Zone 3 feels productive — you're working, you're sweating, you're tired afterwards. But it's too hard to build aerobic base efficiently and too easy to drive the high-end adaptations you get from threshold and VO2max work. Riders who default to tempo on every ride end up moderately fit but never break through. The fix is discipline: easy days genuinely easy, hard days genuinely hard.
Skipping zone 1. Recovery rides feel pointless to competitive personalities. Twenty watts less than yesterday can't possibly help, right? Wrong. Active recovery promotes blood flow, clears metabolic byproducts, and lets your body consolidate the adaptations from yesterday's hard session. If your recovery rides are leaving you tired, they're not recovery rides — they're just easy training rides adding fatigue.
Never updating your zones. Your FTP at the start of a training block might be 230 watts. Eight weeks later, after consistent work, it could be 245. If you're still training with the old zones, your "threshold" intervals are actually upper tempo — still hard, but not driving the adaptation you think they are. Check your zones every four to eight weeks, or better yet, use a coaching platform that monitors your power trends and alerts you when it's time for an update.
Obsessing over the number instead of the training. FTP is a training tool, not a leaderboard. Riders who test every two weeks, chase a higher number for its own sake, or feel demoralised by a bad test result are missing the point. The purpose of FTP is to set your zones accurately so your training is effective. A rider with an FTP of 220 watts who trains consistently in the right zones will improve faster than a rider with an FTP of 280 who does random efforts with no structure.
Ignoring zone distribution. Looking at a single ride in isolation tells you very little. What matters is the pattern across weeks and months. How much time in zone 2 versus zone 3? Are you doing enough high-intensity work? Is your recovery adequate? This is where tracking your zone distribution over time becomes genuinely valuable.
How an AI coach uses your zones
Power zones are useful on their own, but they become significantly more powerful when something is watching the bigger picture for you. This is one of the core capabilities of an AI cycling coach — and if you're curious about the full range of what that means, the article on what an AI cycling coach can actually do covers it in detail.
In practice, an AI coach works with your zones in several specific ways. It tracks your zone distribution across every ride and every week, so you can see whether you're actually following a polarised approach or quietly drifting into that zone 3 grey area. It monitors your power data continuously and can identify when your FTP has shifted — not from a single test, but from the pattern of your best efforts over time. When it prescribes a training session, the targets are specific to your current zones: "3x12 minutes at 95-100% FTP" means something precise and personal. And when you go out and can only manage 90% on a day your legs aren't cooperating, the coach adapts — adjusting the rest of the week to account for the missed stimulus without blowing up your training plan.
The real value is in connecting the dots between your zone data and everything else. An AI coach can tell you that your zone 2 hours have dropped over the past month while your zone 3 time has crept up — and explain why that matters for the base phase you're in. It can spot that your heart rate at the same zone 2 power has been declining, which means your aerobic fitness is genuinely improving. These are insights that exist in your data already. You just need something that's looking for them.
Ready to try it?
You don't need to memorise zone percentages or calculate anything by hand. Connect your Strava account to Veloi, let your ride history sync, and your zones are set automatically based on your power data. From there, you can ask your coach about your zone distribution, get sessions with specific power targets, and track how your fitness is developing across every zone.
Don't have a power meter? That's fine too. Heart rate zones follow the same principles, and your coach can work with whatever data you have. The goal is the same either way — giving structure to your training so that every ride serves a purpose and every week builds on the last. Your data is already telling a story about your fitness. It's time to start reading it.
