Why FTP based training is half wrong

Sorry but they sold you some bad gas

It’s not all bad, workouts designed around FTP are great for aerobic training. They are just poorly optimized for anaerobic workouts.  It’s funny for me to say that since we have a website with 5000+ FTP based workouts. Many or most of these workouts have at least one anaerobic interval.

The anaerobic workouts on the TrainerDay site do provide benefits but if you take your training seriously,  you might want to stop using generic FTP based anaerobic workouts and move to something more individualized. We are offering a new feature to make this simple.

Yes, there is a relationship between FTP and anerobic workouts, but not a strong enough relationship to consider it personalized like they aerobic brother. Because FTP does not individualize these workouts for you, most anaerobic workouts on almost all the platforms will either be too hard or too easy to maximize your potential and save you time.

For most cyclists aerobic training is 90% of the battle, so FTP based aerobic training TRUELY IS the most important part.  Many of us can just stop reading now and keep doing our FTP based aerobic focused workouts and we will be fine.  MTB, cyclocross and many other riders that rely on sprinting power better keep reading.

Ok, for those of you still here, the good news is, once you know your W’ it only takes a few minutes in TrainerDay to customize anaerobic workouts to match your fitness profile. You can easily clean the water out of your gas.

Anaerobic training, intensities and durations.

Let’s state this another way.  Trying to determine how much weight to lift at the gym based on FTP is not likely the best approach.  That is an extreme case example, but I am just saying don’t base your anaerobic training on an aerobic measurement.  This is not me saying this, this is many years of science saying the relationship between the two is very loose.

Pros usually have both large aerobic and anaerobic abilities. For everyone else, the relationship between the two is not so clear.  Great sprinters have large anaerobic ability and some cyclists have very little anaerobic capacity.

So why do we and everyone determine your anaerobic training intervals, based on your FTP?  Because it is simple and in roughly in the ball-park.

To prove what is wrong, let's look at an example

You can ignore below and just see the charts on the right

We have two riders
a) Rider-A with a 200-watt FTP 
b) Rider-B with a 300-watt FTP 

Both riders have the same anaerobic work capacity, their W’ = 20kJ.  These riders with the same W’ but a different FTP should not be doing the same anaerobic workouts based on percent of FTP.

Let me prove that with a slight amount of MATH (I know that is a 4-letter word).  This is all based on established science.  W’ is a fixed amount of energy that you have above your FTP. You can do a fixed # of watts for a fixed amount of time.  Also, to clarify 1 joule is 1 watt for 1 second and a kJ is 1000 joules.

For Rider-A  180% of FTP is 360 watts (FTP+160 watts)
For Rider-B  180% of FTP is 540 watts (FTP+240 watts)

So a 2-minute interval will bring Rider-A to a perfect failure point at 2-minutes (120-seconds) 120*160w = 19.2kJ of energy out of his 20kJ.   (See chart on the right – top)

For Rider-B, 120*240w = 28kJ of energy. 28kJ is much bigger than his 20kJ available, he can’t even get close to completing the two minutes. (See chart on the right – bottom)

We could say these two different riders have two different fitness profiles and need different anaerobic workouts to optimize their training.  

The Solution

The above was a simple example.  When you are talking about multiple intervals with rests between them it’s more complex.  This is where W’Bal saves the day.  It does all this magically for you and tells you exactly how to create the perfect anaerobic workouts designed for you.  It’s very simple in TrainerDay. Once you know your FTP and W’, finding and designing workouts is easy. Continue on to the quick read of our 3-part series on what these terms mean in simplified detail and how it all works.

And learn how to use our new W’Bal Feature

6 thoughts on “Why FTP based training is half wrong”

  1. Hi,

    Why should both riders above have the same W’?
    Isn’t W’ somehow related to CP (FTP)?


  2. Good question, but the answer is NO. There is a relationship between the two but unless you test your W’ then you don’t know. It’s like saying your max HR should be 220-age. For some people it is, but for many people it is not. Also, if you do a long winter base period your W’ usually drops (even more than your FTP) but then your build and pre-race periods build it back up quickly. W’ highly depends on how much recent high intensity work you have done. Most platforms have some way of dealing with this. They might call you a “sprinter” or in the case of Sufferfest they call it your 4dp (4-dimenstional power). We are just talking about 2-dimensional power which is significantly better than 1-dimensional power of FTP when talking about Anaerobic workouts.

  3. Right, so we agree that at lest for comparison we can not also assume W’ to be the same as 20Kj for both.
    Regarding 4DP, I’m a subscriber and imho the concept is good but is missing a 5th dimension: cadence. I’ve got a word from them that this would be taking in consideration more than a year ago but so far nothing…
    The reason I came to this page was exactly to be able to create a Ramp Test to run it on ERG MODE allowing me to pedal in my preference cadence.
    By doing so I was able to reach a much higher CP than using regulars ramp tests where I had to pedal 95 rpm + in order to reach higher levels of power before reaching my max hr.

    Best regards,

    1. Yes, I was just giving two example riders both with 20kj W’ but in most cases the rider with higher FTP would have higher W’.

      I know a few riders that I have a much lower FTP, but I have a higher W’. When choosing a workout and guessing by saying your W’ goes up proportionally is most of the time wrong at some level, frequently fairly large. If you want to build well targeted anaerobic workouts you need to know your W’ OR perform TRIAL AND ERROR. Really trial and error to find the right targeted anaerobic workouts is not a bad approach but using W’ and W’Bal to find workouts can get you a close starting point and save a few weeks of trying to figure it out. It also can motivate you to realize you should be able to complete a specific workout because the math modeling says you should be able to complete it.

      Yes I agree, cadence is the next and important dimension although I can say I don’t know what much about proper cadence, there seems to be too many different opinions. I do know from a pro-coach friend doing some low cadence (45-55) work in Z2 is beneficial and should be considered a core workout.

      So to summarize. FTP tests give a good approximation for up to FTP based workouts. And FTP + W’ give good approximations for above FTP workouts.

  4. Absolutely, trial and error is the key.
    Before power meter I’had wrongly (in my case) persuaded high cadences only.

    Thanks for your prompt responses.

    1. Thank you for opening the question. I wish more people would discuss. My main point should be that you can’t assume any workout in TrainerDay that has intervals that are greater than FTP will work well for you. Possibly this is how I should have written this article. I want to make W’ and W’Bal approachable for people because really it is not much more complex than FTP. Lack of good tests is the problem. I can fix this 🙂 Even with W’Bal you still need trial and error.

      It seems you clearly understand this but for other people, here is the idea below. Start with something you can do (most people should be able to do 140% for 1-minute with 1-minute rests 3 times and each week increase it by 5-10% until they can’t complete it, it’s possible if a rider is hard core TTer without much sprint power and 300w FTP they might not be able to do this, but this should not be so common. After you find your failure, go back and do the previous week and keep increasing just a little each week.

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