Functional Threshold Power (FTP): What it Means to Cyclists

FTP stands for Functional Threshold Power and estimates the highest average power can sustain for one hour, measured in watts. For cycling, FTP is a measure of fitness and an important metric that indicates the amount of work you can sustain for long durations. Additionally, it’s used to determine power zones that are used in training.

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For more information on training with power check out Ask a Cycling Coach Ep 195.

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FTP Definition

Function Threshold Power (FTP) is a measure of your ability to maintain a high but manageable power output for a somewhat lengthy duration. From a physiological perspective, it’s the cycling power you produce when your lactate production has risen, leveled off, and then closely matches your body’s ability to remove lactate. This just barely keeps that lactate flooding at bay. In cycling, FTP is that grey area between the power you can sustain for a very long duration, typically an hour, and the fleeting power you can only tolerate for a couple of minutes.

FTP, on a deeper level, is the balance point between energy supply and demand. Specifically, FTP is the balance between your aerobic and anaerobic energy systems. In general, when you are cycling at low intensities, you are using your aerobic system. The aerobic system uses oxygen to metabolize fuel to create the needed energy. When your aerobic system can meet the energy demands of your muscles, there’s less contribution from your anaerobic energy system.

However, when you are cycling at higher intensities, the anaerobic system contributes more. The anaerobic system metabolizes fuel sources without oxygen and creates energy much faster. As you work harder, the oxygen you can use tops out, even as your leg muscles require more energy, which will begin to overwhelm the anaerobic system. As you continue cycling at high intensities, lactate produced by the anaerobic system accumulates in the muscles. Your breathing ramps higher, your legs start to burn, and your time at this power output becomes very limited.

There’s a harmony between energy systems, and a ‘lactic balance’ is achieved just below the point of overwhelming the anaerobic system. This metabolic steady state, often termed your lactate threshold, actually correlates really closely with your FTP. So much so, that the two terms are basically synonymous.

What FTP Means for Cycling and Training

The primary reason FTP is an important metric that it’s a quantifiable way to measure and track your cycling fitness while providing a contextual framework to gauge the difficulty of your riding and training. Additionally, it serves as the basis of many other power-based training metrics like Training Stress Score and Intensity Factor.

For example, a rider completes an hour-long ride and finishes the ride with a Normalized Power (NP) of 200w. Normalized Power is a mathematically adjusted measurement of average power that smoothes out power spikes and coasting. Still, it really doesn’t tell us much about how hard the cyclist was working compared to their fitness level. Without knowing their FTP, we don’t know if this was an easy endurance ride or an incredibly difficult one.

FTP provides the context. Let’s assume this cyclist has a 300w FTP. That means that they rode at about 66.7%, which is an easier endurance ride. However, if their FTP was 210w, then the difficulty changes dramatically. Instead of an easy ride, they would have been riding at 95%, which a hard thing to do for an hour.

FTP and training

This context is vital for training as well. A structured training plan will progressively train the energy systems needed to grow your fitness. Using cycling power zones, each workout in a plan is designed to provide just enough training stimulus to drive the adaptations that make you a faster cyclist.

By knowing your FTP, you’re able to customize every workout so that you are stressing the right energy systems. In other words, FTP lets you optimize training to your current fitness level. Also, FTP will help you quantify the amount of training stress you are racking up. This is an important metric to track. Too little stress lacks the needed stimulus the body requires for adaptation. Too much, and you’ll overpower the body’s ability to recover. The good news is that TrainerRoad does both for you automatically. 

Why FTP is Important to Cyclists

FTP is significant to cyclists for many reasons. For some, it’s a way to track their growing fitness and for others is a way to compare themselves to other riders. However, FTP comparisons between cyclists don’t tell the entire story because it doesn’t account for power-to-weight, repeatability, and maximum power output.

At the center is its importance for training. An accurate FTP guides a cyclist’s training intensity and reveals the accumulation of training stress. This is vital for training so that it will be hard enough to challenge you while remaining sustainable over time. 

How to Test FTP

An FTP test is a physical assessment, intended to evaluate your cycling fitness. During the test, you attempt to sustain the highest workload you can for a specific duration of time. An estimate of your FTP is calculated from your power output, and from this result, your workouts are tailored to your personal fitness. For the most effective workouts, your FTP should be assessed every 4-6 weeks, so your training plan can keep pace with your current abilities.

Several different formats provide an accurate measurement. TrainerRoad’s preferred FTP assessment is our Ramp Test. The Ramp Test begins with a 5-minute warmup, then every minute thereafter, it gets slightly harder until you cannot maintain target power any longer. 75% of the best one-minute power you achieve during the test is used as your FTP. Our data shows the Ramp Test results in the most accurate and useful test for the majority of riders using TrainerRoad. Since it is quick (normally about 25 minutes) and fairly easy, you can frequently track changes in your fitness.

TrainerRoad training plans include regular FTP tests to ensure that every workout is scaled to your fitness level. At the beginning of every training block, you’ll complete the Ramp Test to ensure the most effective training. Additionally, training plans are designed to increase training stress progressively, thereby providing the stimulus for consistent and lasting fitness gains. Structured training is that stimulus, and stimulus paired with adequate recovery is precisely what you need to get faster.

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For more cycling training knowledge, listen to Ask a Cycling Coach — the only podcast dedicated to making you a faster cyclist. New episodes are released weekly.

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