Power zones, heart rate zones, FTP, and the power curve, a complete guide
"Train in Zone 2." "Your FTP is 250." "Look at your power curve." These phrases show up in every cycling forum, every coach's plan, every training app. But what do they actually mean, and why do they matter?
This post connects the dots: what zones are, how they're anchored to FTP, how heart rate zones differ, and how the power-duration curve reveals what kind of rider you are and what to work on.
FTP: the anchor for everything
Functional Threshold Power (FTP) is the highest power you can sustain for roughly one hour. Dr. Andrew Coggan defined it as the power output at your lactate threshold, the point where lactate production starts outpacing clearance.
FTP is not a goal. It's a measurement, the ruler that sizes everything else. Zones, TSS, IF, training plans, they all reference your FTP as the baseline.
In practice, most people estimate FTP from a 20-minute all-out test (multiply by 0.95), or from their best recent 60-minute power in a race. Some platforms like Atomic Metrix estimate it algorithmically from your ride history, no test required, constantly updated.
Why it matters: if your FTP is set wrong, every zone is wrong. Your "easy" rides might actually be tempo. Your "threshold" intervals might be VO₂max. A 5% FTP error cascades into months of mis-calibrated training. Retest or recalibrate every 6-8 weeks.
Power zones: the 7-zone Coggan model
Once you have FTP, you can slice the intensity spectrum into 7 zones. Each zone has a physiological purpose, it's not arbitrary. The boundaries are percentages of your FTP.
Enter your FTP below and see your personalized watt ranges. Hover each zone to see what it trains.
Your power zones, personalized.
Enter your FTP and see all 7 Coggan zones with watt ranges and training purpose.
Active recovery. Promotes blood flow without adding fatigue.
Aerobic base. Burns fat, builds mitochondria. Where most training time should live.
Moderate intensity. Improves muscular endurance and lactate clearance.
At or near FTP. Pushes the lactate threshold higher — the key limiter for time trialists.
Maximal aerobic power. 3-8 min intervals that increase oxygen uptake capacity.
Above aerobic ceiling. 30s-2min efforts that train glycolytic power.
Max sprints under 30s. Trains neural recruitment and peak power.
A few things worth noting:
- Zone 2 is where you should spend most of your time. It feels too easy. That's the point. It builds the aerobic engine without accumulating fatigue.
- Zone 4 is "the hour of truth." Your FTP is the top of Zone 4. Training here raises your threshold, but it's fatiguing, so dose it carefully (1-2 sessions/week).
- Zone 5-7 are potent but short. VO₂max intervals (Zone 5) last 3-8 minutes each. Anaerobic and neuromuscular work is measured in seconds. Small doses, large impact.
Heart rate zones: the other system
Heart rate zones work similarly but are anchored to your maximum heart rate instead of FTP. The most common model uses 5 zones as percentages of max HR.
The classic formula is 220 − age, but it has ±10 bpm error. The Tanaka formula (208 − 0.7 × age) is slightly better for trained athletes. The gold standard is a max HR field test, ride all-out uphill for 3-5 minutes, the peak is your max.
Heart rate zones
Max Heart Rate
190 bpm
Tanaka formula (208 − 0.7 × age) gives 187 bpm — often more accurate for trained athletes.
These formulas have ±10 bpm error. A field max test is more reliable.
Very light — walking pace, conversation effortless
Easy — can talk in full sentences, this is 'base' intensity
Moderate — conversation gets choppy, breathing noticeably heavier
Hard — can only speak a few words at a time, sustainable for ~1 hour
Maximum — can't talk, legs burning, sustainable for minutes only
Power zones vs heart rate zones
They're not interchangeable. As we covered in our power vs. heart rate post, heart rate is lagged, noisy, and context-dependent. Power zones tell you exactly what you're doing; heart rate zones tell you what it's costing.
Use power zones to prescribe training ("ride at 200-225W"). Use heart rate zones to monitor response ("did that ride cost more today than last Tuesday?"). The gap between the two is where insights live: decoupling and efficiency factor.
The power-duration curve: your fingerprint
FTP tells you one number, your sustained power. But athletes aren't defined by a single number. A sprinter and a time trialist can have the same FTP and be completely different riders.
The power-duration curve (also called a power profile or mean maximal power curve) plots your best power at every duration from 1 second to 60+ minutes. The shape of this curve reveals your rider type.
The power-duration curve
Toggle rider profiles to see how the curve shape reveals strengths and weaknesses. X-axis is log-scaled (sprint → endurance).
Sprinter
Explosive 5-30s power, drops off fast over longer durations
All-rounder
Balanced across all durations — no glaring weakness
Watt values are illustrative for a ~75kg male rider. Your curve will differ — the shape is what reveals your profile.
Reading your curve
Compare your curve to the archetypes above. Where do you sit?
- Steep left side (high 5s-30s): you're a sprinter. Fast-twitch dominant. You win bunch kicks and short punchy climbs. Your limiter is sustained power, base and threshold work will round you out.
- Flat right side (high 20-60min): you're a time trialist or climber. You grind people down on long efforts. Your limiter might be top-end sprint, anaerobic capacity work can add a finishing kick.
- No standout anywhere: all-rounder. Versatile but might lack a weapon. Look at where your curve dips relative to category norms to find your best training investment.
- Everything low: beginner. The good news: training shifts the entire curve upward. Start with base training to lift the right side first.
How the curve changes with training
The power curve isn't static. It shifts with your training:
- Base phase (Zone 2 focus): the right side of the curve lifts, your 20-60min power improves as aerobic capacity grows.
- Build phase (intervals): the 2-8 minute range jumps, VO₂max and anaerobic power respond to targeted intervals.
- Peak / race phase: the left side sharpens, sprint and punch power come up with race-specific intensity.
- Off-season / detraining: the entire curve drops, high-end power fades first, endurance power is more resilient.
Tracking your curve over months (30-day, 90-day, all-time windows) is one of the most powerful ways to see if your training is working. Atomic Metrix calculates this automatically from your ride data.
Practical tips
- Validate your FTP every 6-8 weeks. Training raises it. Illness or breaks lower it. Stale FTP = stale zones.
- Don't obsess over zone boundaries. The body doesn't have hard edges at exactly 75% or 90% FTP. Zones are coaching shorthand, not physics constants.
- Use TSS to compare across zones. 1 hour at FTP = 100 TSS. 2 hours at Zone 2 = ~90 TSS. These become additive building blocks.
- Heart rate drift inside a zone is fine. Starting a Zone 2 ride at 130 bpm and ending at 140 bpm doesn't mean you left Zone 2, heart rate naturally drifts. Check decoupling if you're concerned.
Further reading
- Training and Racing with a Power Meter, Allen & Coggan, Chapters 2-3 define zones and FTP testing protocols.