Threshold Power and Functional Threshold Power

Sorry for being a little naive but, are they the same thing or different? trying to establish some new Power Zones and want to put in the correct FTP etc - I’ve always done average hour power (or 20mins test) then deducted 95% to get FTP setting. Can you please elaborate?

Sorry I meant deducted 5% :slight_smile:

The 95% rule is an “off-the-rack” way of determining Threshold Power (TP) … or FTP … hold this thought for a sec … It doesn’t hold true in a great many cases and this is because people have different High Intensity Energy (HIE) and Peak Power (PP). When you’re outputing power above TP (as in your 20 minute power which is above FTP), how long you can sustain it depends on your HIE mostly and to a very small degree your PP. For example, if you click here for an example:

https://www.xertonline.com/calculator?power_0=260&duration_0=1200&power_1=&duration_1=&power_2=&duration_2=&action=calculate

You’ll see that, the TP is 95% of 20 minute power. But if your 2 minute power was closer to 430, this could be your power duration curve:

https://www.xertonline.com/calculator?power_0=260&duration_0=1200&power_1=430&duration_1=120&power_2=&duration_2=&action=calculate

In this case 100x239/260.3 % or 92% of 20 minute power is TP. This is because, the second athlete has more HIE (and higher PP) than the first athlete. You can experiment with other values that would h ave the same 20 minute power but different TPs. Knowing your HIE and PP together with your TP is vitally important because all the three together determine your training targets, not just TP. See our blog on Paradigm Shift to see the implications.

Now TP and FTP are essentially the same, however if you prefer to have FTP mean 1-hour power, then you can inspect the difference on your power curve (Signature Calculator) and see that your 1-hour power is likely within a few watts of TP.

Remember though, when it comes to personalized training, what is more important is not what your FTP is, but what your own specific targets are. For this, we need to know FTP and HIE and PP.

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Thanks for the reply - all I need are some numbers so that I alter my FTP to reflect new fitness levels. So, how do I find out what these numbers are - my TP is 250 but not sure of the others - any help in the vids on here?

Hi Alan,

If you open Account Settings / Profile tab, you’ll see all three numbers. You can use what Xert has determined as your FTP in other programs. If you keep Xert up-to-date, it may raise/lower your FTP as new data arrives. Being sensitive to subtle changes coming from your data sets Xert apart.

If you use Xert’s workouts, they will use FTP as well as your other numbers to set workout intensities and duration. This is a unique characteristic of Xert and what many that are advocating for its use have begun to realize. Proper training requires more than knowing your FTP and Xert helps you trainer smarter.

Good luck!

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Again, thank you for your reply. Looking at My Fitness, the last last workout I deed yielded a PP of 505, HIE of 14 and TP of 248, so am I safe to update my Garmin FTP setting to 248 to reflect new zones? incidently, Garmin had the hour power down as 234w. I know putting 248, any intervals done after will be much harder to do and perhaps complete where as currently I have Garmin set on 227 - just trying to progress is all I’m after. I understand my FTP can fluctuate but I need a ball park figure to work from,

Alan

No worries. I had a look at your progression data and it appears that Xert is basing these numbers on your latest 30-30 workout. You hit MPA at around 410W which would put a high dependency on an accurate Peak Power as it is pretty close to 505W. There haven’t been any efforts to date where you’ve demonstrated a good Peak Power so the current number of 505 is a rough estimate. If your Peak Power is closer to 700, for example, you may see your FTP come down by as much as 10W or so. 505W is generally on the low side so I would go with, say, 240W for the time being until you put in a good peak power effort. Once you have that data, if it is much higher than 505W, check the FAQ on how to seed your progression so that you can apply this new information to all your previous activities.

Let us know how things go and we can help you adjust accordingly. Good luck!

Thank you for the time and effort in your replies. I’ll try the 240W for now and see how I cope with the next 4 weeks of HIIT :slight_smile:

If your PP and HIE are at 505 and 14, respectively, you may find the intervals that are a high percentage of FTP to be quite hard and those that are a low percentage of FTP to be ok. If you’re using another system, you may want to transcribe these into our Workout Designer to see how you’d cope. Also, much will depend on your true Training Load. if you’ve only just started training, they will feel a lot harder in general. You’ll need more accumulated TL before you’ll handle the added load from the HIIT.

I went to My Fitness, and there is no Advanced tab - can you elaborate on where to find these three numbers? Thanks!

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Account Settings / Profile

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