Fitness Signature Accuracy - Test?

Don’t call it quits. When you feel you are close to your limit keep pedaling as hard as you can for as long as you can. If the power that you can deliver is not above TP then yes you can stop at that point.


Yes! This is the point of Xert, and why standard “tests” aren’t required. We dont care about mean power at all. Instead, we’re looking at your power, relative to MPA, at every second in time. Any time you’re producing work above TP (especially when MPA is pulled down close to TP), it helps the extraction algorithm get a more accurate fitness signature - we go into more detail on this in an upcoming podcast! Stay tuned :slight_smile:

During the Breakthrough Test v2, at the end of the interval time, my Trainer control drops the power drastically and so very little power (less than 100w) is generated even at very high cadence. Is it actually possible to maintain the power even when The trainer is in control or should I switch to a different mode and ignore the rest of the test till I can no longer continue and then stop there?.

“During a steady-state, fixed power effort above threshold, from fresh to failure, an athlete starts with an MPA that is peak power and MPA reduces to eventually become equal to the fixed power value. MPA represents their limit at any given moment and at the point of failure, their power equals their limit. Thus a point of failure can also be viewed as a point of maximal effort . The duration at a given point in time to the point of failure, is often called time-to-exhaustion (TTE) and it represents the time it will take the athlete to reach failure.”

Just for the purposes of roughly checking the the fitness signature based on what Xert gives me as TTE, could this approach be ok for a quick check from time to time?.

Overall I think my signature is now representative and hopefully Xert suggested workouts appropriate.

You can push for a BT at any time to test the validity of the fitness signature. What we dont require is a steady-state, fixed power effort. We can capture the same information (perhaps even better) by looking at non-steady state efforts, or by looking at what happens after you reach the limit of tolerance at a fixed power (example below):

Hold 500W until you can’t anymore - lets assume that’s 1 min. At the end of that minute you’re tired, but not completely exhausted. You simply can’t hold 500W because you’ve become limited by MPA. You can continue to produce power above Threshold, but it has to be less than 500W now (and will continue to drop as MPA drops). How you fatigue after that initial point of failure gives a LOAD of information that isn’t captured in traditional testing protocols. Hope that makes sense.


that makes so much sense… I am just so pre-programed to go for x minutes then quit… ever since I started cycling i need to call my wife up and have her cheer me on… tell me to keep pushing… at that moment when i feel like i can’t hold 500 watts… or whatever.


A good point which I didn’t think of as I have only done it out on the road. I guess next time you have to keep that in mind and push with 30 seconds to go. I wonder if the the SMART function just cut the effort short in that case???

I adjusted the Version 2 breakthrough test adding a 5 minute, 120% interval to the end to make this custom workout which would get around that… I think? because it gives you an indication that you should just keep pushing, and i would think once you are really truly unable to pedal above the preset TP you would probably easily remember to quit and you could hit the next interval button on the workout player to move past it once you quit pedaling…
does this look like a good idea? it’s just a straight 5 minute interval…

Yes, do something similar for trainer-controlled breakthrough workouts I.e. just extend the final interval for an extra 5 or 10 minutes in a custom workout. Then skip the rest of the interval on failure. Especially when it’s been a few weeks of normal decay, I can complete the ‘final’ interval with something in the tank.

Another option I’ve tried is to increase the intensity by 10% or so during the final interval if it’s feeling easy… if you do that after the ‘original’ interval duration, it’s like creating another ramp step… and at least you hit failure sooner.

Or you can turn trainer control off and then you drive the intensity… find it’s better to do that from the beginning, rather than during a workout as it can take time to find the right gear and resistance…

Yes that is a good idea.

If I knew how, I would add a second ‘Push a last time’ interval and make it smart to detect when Xert has dropped me e.g my power drops to 110% TP and then drop my power to ‘recover’ so that I continue with the remaining intervals without manual interventions.

A side Question. How do data from Xert compare to other smart trainer tests using the same equipment for both at the same time?.

I had a 129w critical power(@critical heartrate) and TP=214w from myEtraing app and TP=131w from Xert. Same data/equipment source.

so, I want to feed the WKO5 power duration profile and I wonder about Xert’s current fitness signature for me too. It just doesn’t make sense to me how Xert can know my hour power based on me doing a 5 minute breakthrough effort. I have no longer duration breakthroughs in my history. (I really have never tried to sustain FTP more than 20 minutes… though I really think it would be a good skill for me to have overall) real knowledge and belief in an actual maximal effort that I can sustain… what is my wall that I should try to never go over when doing hard efforts… If i want to not blow up.
To that end…
i’ve decided to do a Kolie Moore style FTP test

If my current Xert fitness signature is 277 TP, and I manage to go around 50 minutes at 299 watts average will that sort of breakthrough change what Xert thinks my signature looks like? For example, lower PP and/or HIE and raise TP? or do all breakthroughs always raise ALL aspects of the signature or just raise one or two of the three while leaving the 2nd/3rd right where it is?

I still believe in the idea that aerobic and anaerogic engines are contributing to the work load…

To the best of my knowledge. Yes that sort of effort could bring TP up and HIE down. Actually all breakthroughs can in theory do that. Xert will try to match the parameters to their values that better fit the effort. This could mean that some of them go down and some up. Going 229W for 50 min when your TP is 277W seems optimistic if your current signature is accurate.

“optimistic” meaning… that it’s not likely that i could go 249W for 50 minutes? lol challenge accepted

After re-reading I see obviously that was a type-O… anyways… yeah my plan is to go 277W for the initial 10 minutes in ERG… then i’m maybe turning off ERG and riding by feel and watching my watts for the rest of the test… we’ll just see… going right now… lol

Typo: it should read 299 as per your post…

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that was both interesting and informative… I went until I couldn’t… and I didn’t bother turning off ERG…
I believe the Xert MPA graph in that I probably did have more to give, but It’s just me doing a 5 star difficulty workout while i’m 2.3 star athlete and I’ve been doing workouts no harder than 2.5 stars all of 2020 so far… so it makes a lot of sense that I really wouldn’t be breaking through under this kind of test…
Soo to summarize, I think I finally trust the Xert fitness signature…

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Hmmm… Interesting :wink:

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Are these Test Workouts meant to be done with ERG mode off? Or does the Trainer in Auto mode disable ERG Mode according to the nature of the interval?


The version 3 workout says the following so with erg on I guess…

This workout is intentionally designed to help you achieve a fitness breakthrough on your smart trainer using trainer control.

I’m thinking about giving it a go today as its been a while since I did any sort of breakthrough workout.

Version 3 looks hard!

They all look far too difficult to me :weary:

So I did the Fitness Test (Version 1 I think). Got a 22.3% increase in PP but a 2.1% decrease in TP. I had more to give. After the 4th threshold does it switch off ERG mode? Am I supposed to change through my gears and push on to maximal fatigue?

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