What Is FTP in Cycling? How to Test and Use Your Threshold Power

FTP (Functional Threshold Power) is the maximum power you can sustain for approximately 40 to 60 minutes. It marks the boundary where your aerobic system can no longer keep up with the energy demand, and anaerobic metabolism kicks in to fill the gap.

But here's the thing most apps won't tell you: FTP is a calibration tool, not a performance trophy. Its purpose is to set your training intensities correctly. Nothing more, nothing less.

The Two Thresholds Your Body Actually Has

Before we talk about testing, you need to understand what's actually happening inside your body. There are two real physiological boundaries. Not five zones, not seven zones. Just two thresholds.

First threshold (aerobic)

The first threshold is the intensity where your body starts producing more lactate than it can metabolize inside the muscle cell. Blood lactate levels rise slightly above resting values. This threshold also marks the point of maximum fat oxidation per minute.

Below this threshold, you're in easy territory and you can ride for hours. Above it, fatigue accelerates significantly. The first threshold typically sits at around 65-75% of VO2max and 80-90% of FTP.

At a practical level, this first threshold marks the transition between the low, cruising rhythms you can maintain for several hours and a medium effort where fatigue builds noticeably faster. You can sustain first-threshold intensity for 2 to 3 hours, depending on your glycogen stores and fitness level.

Second threshold (anaerobic, where FTP lives)

The second threshold is the intensity range where aerobic metabolism alone can no longer sustain the activity, and anaerobic energy production steps in to help.

This is also the point where lactate production rises exponentially in an incremental test. Fats become a minority fuel source: most energy now comes from oxidizing carbohydrates in the mitochondria. Above this threshold, phosphocreatine and cytoplasmic glycolysis complement aerobic metabolism to meet the extreme energy demands.

Above the second threshold, oxygen consumption and heart rate don't stabilize. If you continue long enough, you'll reach your maximum oxygen consumption, maximum heart rate, and exhaustion.

How long can you hold it? The second threshold can be sustained for approximately 40-60 minutes maximum, and less time the further above it you go. This is your FTP zone.

You can estimate this second threshold with good precision through critical power calculations or by extrapolating from long tests of more than 15 minutes, applying a correction factor.

The Tests NUA Uses

NUA schedules tests as part of your training plan at strategic points, and you can also request one at any time through the coach. All tests can be done indoors on a trainer or outdoors on the road.

FTP test (steady-state)

The classic. A sustained effort of approximately 20 minutes where you aim to produce the maximum average power you can hold. NUA analyzes your peak power across multiple windows (12 to 20 minutes) and applies duration-specific correction factors to derive your FTP.

The key to a good FTP test is pacing by feel, not by numbers. Don't set a target power because it will influence you. Do the test by perceived exertion without looking at your computer.

Here's the pacing guide:

Segment	Duration	RPE (1-10)	How it feels
Start	First 10 minutes	8/10	Hard but controlled. You could go harder but you're holding back.
Middle	Minutes 10-16	9/10	Very hard. You're questioning your life choices but still holding form.
Finish	Final minutes	Maximum	Everything you have left. Empty the tank.

The most common mistake is starting too hard in the first 5 minutes and blowing up before the end.

Ramp test

A progressive test where intensity increases every minute until you can't hold it anymore. NUA takes your peak 1-minute power and multiplies it by 0.75 to estimate FTP. The ramp test is shorter and less mentally demanding than a steady-state test, which makes it a good option if you dread the 20-minute all-out effort. The tradeoff is slightly less precision.

Anaerobic capacity test

This test measures your short-duration power peaks: P1 (peak 1-minute power) and P6 (peak 6-minute power). Unlike the FTP and ramp tests, which can be done with just a heart rate monitor or even by RPE alone, the anaerobic capacity test requires a power meter. The reason is simple: heart rate can't respond fast enough to capture 1-minute and 6-minute peak efforts accurately. By the time your heart rate stabilizes, the effort is already over.

NUA uses P1 and P6 for two things:

1. Prescribing high-intensity intervals. For efforts above FTP (zone 5 and above), FTP is no longer the right reference. NUA uses your P1 and P6 to set accurate power targets for short, explosive intervals.
2. Estimating your anaerobic battery (W'). From P1 and P6, NUA calculates your Critical Power and W-prime: the total amount of work you can do above your threshold before you blow up. This determines how NUA distributes effort across intervals and how much recovery you need between them.

The anaerobic test is optional and can always be skipped.

Do I have to test?

No. Tests are useful but not mandatory. The FTP test and ramp test can both be done without a power meter, guided by heart rate or RPE. If you already have baseline stats from your heart rate monitor, you can skip the FTP test entirely. NUA will ask if you want to skip or proceed.

During your first week, and until you complete a test, training will be based on heart rate or RPE. If you don't want to test on your scheduled test day, you can replace it with an aerobic maintenance session. Just tell NUA.

How to Interpret Your Results

This is where most cyclists get it wrong. The purpose of the test is to determine adequate training intensities. It is not a direct estimation of your performance.

Test results can vary up or down based on factors like motivation, nutritional state, recovery status, temperature, or altitude. A bad test doesn't mean you're unfit. A great test doesn't mean you're ready to race. It means your training zones are now calibrated.

The objective is better training, not a bigger number.

What Happens When Your FTP Is Wrong

Having an overestimated FTP has real consequences that compound over weeks:

1. Overtraining: Your power targets are too high, so you work harder than necessary and don't achieve the intended physiological adaptations. You're accumulating fatigue without the benefit.

2. Premature peak: You reach your maximum form too early, leaving you exhausted for your actual target event.

3. You can't hit the numbers: When target power is above your real capacity, frustration builds as you consistently fail to complete workouts as prescribed.

4. Invisible fatigue: Without an accurate FTP, fitness, form, and fatigue metrics are all distorted. You feel like you're not training enough when you're actually overcooked.

If your FTP is overestimated, update the value immediately. Training with wrong numbers is worse than training with no numbers at all.

How NUA Uses Your FTP

NUA's approach to thresholds is different from what you'll find in most training apps.

We don't use training zones to prescribe workouts. Physiology is a continuum. There's nothing magical in the transition from one zone to another. The effort at the top of zone 2 is more similar to the bottom of zone 3 than it is to the bottom of zone 2. Zones are artificial constructs that we use to categorize intensities under the same labels, but they're not physiological.

Instead, NUA uses percentages and percentiles (%FTP, %HR threshold) to set training intensity. This gives us precision that zone-based systems can't match.

Here's what happens with your thresholds in NUA:

• Auto-detection from any ride. NUA doesn't wait for a formal test. It analyzes your peak power across multiple time windows (12 to 20+ minutes) from every ride you do, and applies duration-specific correction factors to estimate whether your FTP has changed. It does the same with heart rate data. If it detects a meaningful shift, it flags it and updates your upcoming sessions. This works with both hard data from your power meter and wearables, and perception data from your RPE reports.
• Guardrails to prevent false positives. Not every strong effort means your FTP changed. NUA limits automatic estimations to twice per week for the same metric, rejects estimates where anaerobic depletion was too high (meaning you were sprinting, not sustaining), and never overrides a value you've manually set.
• No manual zone configuration needed. You don't need to set up zones in Garmin Connect. NUA handles everything through the workout targets it sends to your device.
• RPE as the gold standard. After every workout, NUA asks for your Rate of Perceived Exertion, both average and maximum. RPE is the indicator that best correlates with the physiological stress your body has experienced. According to the latest studies and meta-analyses, RPE sits a step above traditional measures like heart rate or power, and far surpasses load measurements based on time or distance.
• Three guidance modes. Every session can be guided by power (watts), heart rate, or RPE. If you don't have your sensors available one day, you can switch the session target without losing training quality.