The assessment - Functional Threshold power

The Assessment Aerobic test tests for your functional threshold power (FTP), which is the power you can maintain in a quasi-steady state without fatiguing.

"...the power you can maintain in a quasi-steady state without fatiguing."

that doesn't mean...

  • For an hour.
  • For 2 minutes. 
  • For 20 minutes.

It's based off of this:

The duration for which you can hold your FTP is individual.

Oh, and also, you can train:

  • Your absolute FTP number.
  • The duration with which you can hold your FTP.
  • Your ability to repeatedly generate power at FTP day to day.

But I'm getting ahead of myself.

FTP is the anchor point in your power duration curve used to determine your training zones. Training zones describe the intensity at which you’re training. Zone systems can be complex or straightforward, but they all have one thing in common – they describe how hard you should train.

Above the dotted line = borrowed time; Below the dotted line = all the time.

We use FTP as the anchor point for your zones because it represents an important physiological turning point – the point at which your body cannot meet energy supply with energy demand. To continue to meet the work (pedaling) demands, your body has to tap into the anaerobic system to supply extra energy, which rapidly causes fatigue. Eventually, your body cannot maintain intensity.

The anaerobic system cannot indefinitely supply that energy without a cost. Biochemically, drawing on the anaerobic energy pathway eventually changes your body’s acidity as a byproduct of using lactate for fuel, which interferes with muscle contraction – they can no longer fire at the same rate. Subjectively, this is the ‘burning’ you feel when you ride really, really hard.

Anyway, how do you determine your FTP?  Here’s how:

the Assessment FTP Protocol:

I prescribe the 5 minutes VO2 max effort because a genuine 5-minute all-out effort recruits your anaerobic system to produce energy. If you perform the VO2 max correctly, spin lightly for 5 minutes, and then complete the 20-minute effort. The watts you sustain more closely represent your true aerobic contribution.

For example, some cyclists have an incredible anaerobic capacity which can add 20+ watts to their 20-minute effort! If they took this test without performing the 5-minute attempt, they would have an anaerobically inflated FTP number which would produce inaccurate training zones. Every workout they executed with those zones would be slightly too challenging with the long-term risk of accumulating too much fatigue, to the detriment of their performance.

  1. After a warm-up, go as hard as you can for five minutes.
  2. Spin easy for about 5 minutes to flush the lactate out of your legs, and then go as hard as you can for 20 minutes.
  3. You’re done. Ride home or keep on riding. It’s your life.

How to Screw this up:

  1. Don’t go hard enough on the 5 minute VO2 max effort because you fear the 20-minute effort.
  2. Don’t eat carbohydrates before the workout. 
  3. If performing outside, pick a section of road with intersections, so they have to stop.
  4. Pick a climb that won’t take you 20 minutes to climb. 
  5. Have a ‘number’ in mind that’s wildly optimistic and causes you to blow up 8 minutes into the test.

I've prescribed this test at least 💯 times.

My observation is that the worst outcome is if an athlete does not finish the 20-minute test. While this seems insignificant, not completing the aerobic test is a cardinal sin because:

  1. We structure the training to test under similar training loads. The window to do so is finite before the act of testing interrupts training momentum. 
  2. It demoralizes the athlete. They feel they have unfinished business and want to repeat the test.
  3. Bombing the test doesn’t provide data on fitness progression. Therefore, it’s unclear if the training works or what adjustments should be made. 

So how should one mentally approach and physically pace the Aerobic Assessment?


Ironically, don’t approach this like your last day on Earth.  This is just a test, not a reason to dig for a new pain level and cough up blood. If you’re significantly fitter than in the past, you won’t have to kill yourself for it. The power will be there. 



For pacing, use a combination of data and sensation. Start both the 5-minute test and the 20-minute test with a conservative power number, and after a couple of minutes, let sensations dictate effort. Stop looking at your device and focus on the feeling of going hard. 

How to Analyze your Results

Once you’ve obtained your results, it’s time to break down the numbers:

  1. Upload your file to TrainingPeaks (or whatever you use to analyze).
  2. Take the average power (NOT normalized) from the 20-minute effort and multiply by 93%. That’s your FTP.


20-minute average power 258. 

258 * .93 = 240 (round up)

How to interpret your results

If you want to compare your FTP to others, you could take your watts’ absolute value, but it wouldn’t tell you that much because it doesn’t account for differences in body mass.

To account for body mass differences, take your FTP from above and divide it by your weight in kilograms.

FTP: 240
Weight: 150 lbs; to convert to kilograms, divide by 2.2.

279/(150/2.2)) = 3.5 w/kg.

Since you’re curious, you can pull up the TrainingPeaks Power Profile dashboard chart to see how your w/kg compares to a representative data set of different road racing categories.

How to screw up your FTP interpretation:

FTP test interpretations are fraught. They carry the weight of fifteen years of endurance coaching baggage, so it’s easy to get caught up in misinformation and lose perspective. 

  1. Equate your worth as a cyclist to your FTP. As your net worth, your FTP is a simple, elegant number that neatly expresses not just how fast you are but your value as a human being.
  2. Think that one test speaks to your potential as a cyclist.
  3. Obsessively compare your numbers to other cyclists.
  4. Think that your FTP alone will win races.

So how should you think about your FTP?

In general, think of your FTP in neutral terms – it is a data point you use to establish zones and one way you can measure fitness progression.

So how much can I improve my FTP?

Probably a lot, but it’s hard to say. Remember, talent is real, and life isn’t fair. Some people do start at a superior level.

Above all, however, what drives FTP progression is committing to training well for a long time. Saying so doesn’t give people enough context to know what I mean, so I’ll frame this differently.

A professional cyclist trains anywhere from 700 to 1200 hours a year, and they’ve done so for years and years. If you’re starting to train, what makes you think you should be able to produce the same numbers they do after a couple of months of structured training?

You won’t. So if your FTP test didn’t go the way you wanted it to go, don’t call up your mom and dad and yell at them for not giving you the ‘fast FTP genes.’ Get to work. Unlocking your genetic potential takes years of consistent, quality training.

"You're just saying that and can't point to one example of someone's FTP dramatically increasing under your coaching."

I call your bluff and Raise you the Great Dane. You don’t know what your potential is, and neither do I. You’ll never know how fast you can get until you do the work.