Functional Threshold Power: What you need to know

Functional Threshold Power (FTP) is one of the most useful, objective training metrics available for cyclists. It measures the maximum amount of power that an individual can produce across an extended period of time. That period of time is usually defined as one hour.

From a physiological standpoint, FTP marks the power or effort that you can hold where your lactate levels are being used and buffered effectively and not flooding your system.

When exceeding your FTP you may experience sensations of rapid or increased respiratory rate and your body’s inability to get the amount of oxygen that it needs to function optimally (or aerobically).

While other metrics such as heart rate can also denote the change from aerobic to anaerobic work rate, FTP is an objective measurement, whereas heart rate is influenced daily by a myriad of subjective factors.

Why Does FTP Matter?

FTP is the central guiding metric for lots of other data that coaches and athletes use to analyze training. FTP is used in calculations such as Training Stress Score (quantifying the stress that training has on your body), Intensity Factor (quantifying the intensity of the training), Chronic Training Load (measuring stress over time), Form (measuring how fitness and fatigue are balancing), and so much more.

FTP also allows athletes to set up “training zones” or powers that indicate what improvements or energy systems we are targeting with intervals or training rides.

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

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

No matter how fast or how slow you may categorize yourself, working at a specific percentage of your personal FTP will challenge people similarly. 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’ll probably get a whole host of very passionate opinions. People seem to feel strongly about the way that FTP should be measured.

The truth is, FTP is just a training metric and can be measured a few different ways. While a high FTP may give you big bragging rights, when it comes to race day, you’ll need to prove it all over again. If you cheat an FTP test it brings up the old saying that your high school coach used to tell you, “You’re only cheating yourself.”

That said, the ‘right way’ to do an FTP test is the way that makes you feel the most confident, allows you to get 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 that you can hold for one hour, it makes sense that it could be measured by a one hour test.

While this would be the most technical take on the concept of FTP, I personally find the concept flawed. The one hour test is very difficult to execute for most people. Finding terrain that allows you to pedal consistently for one hour can alone be difficult. It’s also difficult to mentally squeeze your best ability out of yourself for that duration of time.

Finally, the idea that you could produce your best result in a one hour solo test is a bit of a stretch, when adrenaline on race day could squeeze out a few percentages as well. That said, if you find yourself a purist, or a master of suffering, this is a perfectly acceptable way to test FTP.

2. 20 Minute Test: Probably the most common way to measure FTP is through a 20-minute test. This is the maximum amount of power that you can consistently hold for 20 minutes. Then to get your FTP, you will multiply that average power by .95.

Twenty minutes is usually a very digestible amount of time for people; however, the only downside to this testing type is that in order to pace well you need to have some relative 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 usually they involve wattages increasing every minute throughout the test, and the athlete continues until failure and then a percentage of their maximum power will determine FTP.

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

4. Lab Test: FTP can also be determined through a laboratory setting using any of the above protocols with a ventilatory mask and/or blood draws in order to help further validate where your threshold lies.

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

5. Computer Estimates: Some brands have begun doing computerized FTP estimations. 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 great for anyone who struggles with testing anxiety or feels they don’t have the time to spend testing. Computer estimates are great to gain an FTP that will give you accurate enough training metrics, but your friends will probably not allow that metric to fly when comparing values.

Furthermore, it’s important to note that not allow software are created equal on this front and you’ll need a big enough data sample for the computer to analyze.

When Should I Measure FTP?

Since FTP is used to help you set up the best training zones possible, FTP should be measured every time you think you have had a significant or meaningful change in fitness.

That means FTP tests are especially important after an extended off season or for a new cyclist just learning their abilities. A beginner cyclist should also test more frequently because they will likely experience gains more rapidly. A beginner cyclist should test every 4-8 weeks to map progress.

If you do not test and continue to use old training zones, then you may not be challenging yourself enough. In the same way, if you detrain and use old training zones then you may be pushing yourself too hard.

A seasoned cyclist may not need to test as much as a beginner because large gains may be harder to come by. This is a circumstance is which a very attentive coach or computer can help measure and detect small gains.

Just a Snapshot

It’s worth mentioning that FTP is just a snapshot of your fitness.

While a high FTP can make many things in cycling easier, it also doesn’t give an entire picture of strengths and weaknesses. In the same way, an FTP test is your ability in a single effort on a single day and cannot encapsulate all of your improvements or abilities.

An athlete may carry fatigue from one training session into the next and struggle to meet numbers that his or her FTP indicates would be possible. That single snapshot is not a reason to alter FTP, re-test, or panic. It is simply a data point. The best thing we can do as students of this sport is track data points, notice patterns, and rejoice in improvement.