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.

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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.

Get a Deeper Understanding

And learn how to use our new W’Bal Feature

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