Functional power threshold: what you need to know


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Functional Threshold Power (FTP) is one of the most useful and objective training metrics available to cyclists. It measures the maximum amount of power an individual can produce over an extended period of time. This period of time is usually defined as one hour.

From a physiological perspective, FTP marks how much power or effort you can sustain where your lactate levels are being used and buffered efficiently and not flooding your system.

When you exceed your FTP, you may experience feelings of rapid or increased respiratory rate and your body’s inability to get the amount of oxygen it needs to function optimally (or aerobic).

While other measurements such as heart rate can also indicate the shift from aerobic to anaerobic work rate, FTP is an objective measurement, while heart rate is influenced daily by a myriad of subjective factors.

Why is FTP important?

FTP is the central benchmark measurement for many other data that coaches and athletes use to analyze training. FTP is used in calculations such as Training Stress Score (quantifying how much stress training puts on your body), Intensity Factor (quantifying training intensity), Workout Load chronic training (measuring stress over time), fitness (measuring how fitness and fatigue balance out), and more.

FTP also allows athletes to set up “training zones” or potencies that indicate the improvements or energy systems we are targeting with training intervals or journeys.

Additionally, it provides a metric that we can measure to monitor improvements.

Finally, FTP allows us to connect with each other through relative difficulty. For example, 200 watts may be very difficult for one athlete, but relatively easy for another. We can relate by discussing a percentage of our FTP.

No matter how fast or slow you can categorize yourself, working at a specific percentage of your personal FTP will challenge people in the same way. That said, you can train yourself to become more efficient at higher percentages of your FTP with specific training.

How can you measure FTP?

If you ask this question on a group ride, you’re likely to get a whole host of very heated opinions. People seem to be very attached to how FTP should be measured.

The truth is that FTP is just a training metric and can be measured in different ways. While a high FTP might give you bragging rights, on race day you’ll have to prove it again. If you cheat on an FTP test, it’s reminiscent of the old saying your high school coach used to tell you, “You’re just cheating.”

That said, the “right way” to perform an FTP test is the one that gives you the most confidence, gets you the most accurate result, and allows you to dig the deepest. The following have all been touted as acceptable FTP testing strategies:

1. Hour test: Since FTP is theoretically the absolute best power you can sustain for an hour, it makes sense that it could be measured by a one-hour test.

Although this is the most technical version of the FTP concept, I personally find the concept flawed. The one hour test is very difficult for most people to perform. Finding terrain that allows you to cycle steadily for an hour can be difficult on its own. It’s also hard to mentally leverage your best abilities during this time.

Finally, the idea that you can produce your best result in an hour-long solo test is a bit of a stretch, when the adrenaline on race day could also knock some percentages off. That said, if you find yourself a purist or master of suffering, this is a perfectly acceptable way to test FTP.

2. 20 minute trial: Probably the most common way to measure FTP is to perform a 20 minute test. This is the maximum power you can sustain for 20 minutes. Then, to get your FTP, you would multiply that average power by 0.95.

Twenty minutes is generally a very digestible time for people; however, the only downside to this type of test is that in order to pace well, you need to have some awareness of what this type of effort should feel like.

3. Ramp test: Ramp tests are also popular because they are engaging and palatable.

I’ve seen several different types of protocols for tests like this, but they usually involve powers increasing every minute throughout the test, and the athlete continues until failure, then a percentage of their power maximum will determine the FTP.

This type of testing must be done on a stationary bike because following exact protocols elsewhere would be very difficult.

4. Laboratory test: FTP can also be determined in the lab using one of the above protocols with a breathing mask and/or blood draws to help further validate where your threshold is.

For most amateur athletes this is a very expensive and unnecessary form of testing, but for the true science enthusiast or a professional it can provide the additional information needed for marginal gains.

5. Computer estimates: Some brands have started doing computerized FTP estimates. This means that you can train for a set period of time and based on your results and training an algorithm will determine your FTP.

This method is ideal for anyone who struggles with test anxiety or feels they don’t have time to take tests. Computer estimates are great for getting an FTP that will give you reasonably accurate training metrics, but your friends probably won’t allow that metric to fly when comparing values.

Also, it is important to note that software is not created equal on this front and you will need a large enough data sample for the computer to analyze.

When should I measure FTP?

Since FTP is used to help you set up the best possible training zones, FTP should be measured whenever you believe you have had a significant or significant change in your fitness.

This means FTP testing is especially important after a long off-season or for a new rider who has just learned their abilities. A beginner cyclist should also test more frequently, as they are likely to experience faster gains. A beginner cyclist should test every 4-8 weeks to chart progress.

If you don’t test and continue to use the old training zones, you may not be challenging yourself enough. Similarly, if you detrain and use old training zones, you may be pushing yourself too hard.

A seasoned rider may not need to test as much as a beginner because big gains may be more difficult to achieve. This is a circumstance in which a very observant coach or computer can help measure and detect small gains.

Just a snapshot

It should be mentioned that FTP is only a snapshot of your fitness.

While a high FTP can make a lot of things easier in cycling, it also doesn’t paint the full picture of strengths and weaknesses. In the same way, an FTP test is your capacity in a single effort over a single day and cannot sum up all your improvements or abilities.

An athlete may be fatigued from one workout to the next and struggle to hit the numbers their FTP indicates are possible. This single snapshot is no reason to modify the FTP, re-test or panic. It is simply a data point. The best thing we can do as students of the sport is to follow the data points, notice the patterns, and rejoice in the improvement.


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