How to breakthrough indoors

How should I approach testing for BT indoors? I moved to train inside recently, switched from single leg PM to Neo and I think my MPA is a bit high. Some workouts with difficulty 3 (particular Higher Ground types) are almost impossible to complete, they feel like a ramp test. My TL is 4 stars.

I am thinking of the following steps:

  • Clean drivetrain to minimize losses :slight_smile:
  • Select a recent hard activity and use its signature.
  • Set decay method to Optimal.
  • Perform BT test v3.

Is there anything I am missing?

Like many, you may not be able to produce as much power indoors as outside. Dehyrdation, heat build-up, mental attitude can all be part of that reason.
As you suggested you could manually adjust your signature downwards - maybe by 5% and let it settle down for a few workouts and see how things go.

Cleaning your drive train is never a bad thing but I cannot see it making that much of a difference.

Have you run the power meter side by side with the neo? Maybe the power outputs are different.
I used to use a stages, and the occasional spikes in power it gave me would give me a very high MPA, something like 2000. So I found the activities with those high Watts and flagged them. That brought my MPA down to where it should be.

Well, I just want to establish new signature for the Neo trainer.

It may be worth considering doing a 20 minute test and a 120 second test on the trainer. Make these full-on efforts. Don’t worry about doing anything other than a warm up and a single effort (no 5 minute effort before the 20 minute effort as in the classic FTP test).

Pacing isn’t important although a good even effort is needed. If you don’t make it to 20 minutes don’t worry but it should be a max effort. Same with 120 seconds.

After you’ve done both tests you can plug the 2 values into the Power Curve Calculator and get a new signature based on these indoor efforts.

If it’s not quite right it’ll soon decay enough that you’ll get a breakthrough at some point.

A couple of things to watch out for:

  • Unless you test/breakthrough regularly you’re signature will decay and will not reflect your abilities. There are a few breakthrough workouts in the library to help with this. I personally like a MAP test: 100W + 25W/min until failure. It’s short enough to be less affected by heat buildup and it’s not that stressful on the body.

  • If you venture back outside there’s a good chance you’re going to boost your signature just with a fairly good effort, especially if your PM and the Neo aren’t that close. It will also depend on how close your indoor and outdoor power is.

Hope that helps.


Mike, you say to consider 20 minutes effort + 120 seconds test. Also a MAP test (is it the ramp pyramid until failure?). Which one would give more accurate signature?

I have had several BT indoors. It’s never easy, either in- or outdoors, but my indoor BT’s always occur during a steady near max effort over a sustained period.

I.e. when (virtually) climbing a big mountain at grades of 8% average, or similar. I just look at MPA and I will either deplete that (to TP) or get it down so far, that I can put in a short sprint effort to a BT.

While I agree that in general riding indoors is harder than outdoors, I never adapt my (F)TP to reflect that, but Xert may eventually lower it by itself. It’s mostly a matter of cooling, hydrating (up to a 600 ml bottle per hour extra) and mental strength.

I find that having a real life video (Tacx Neo with Tacx TDA subscription) motivates me best. I hate the Zwift cartoon network…

The 120 second + 20 minute tests are for creating a new signature.

The MAP test is good for maintaining it, and yes, it’s the ramp to failure. I like the British Cycling version. Here’s my custom workout. Not sure if there’s an easy way to share that with other users.


I think it’s important to have very good cooling with as much airflow as possible. That’s probably the biggest differentiation between indoors and outdoors.

Even with good airflow I always struggled with overheating during harder efforts until I started doing endurance workouts with no ventilation. After that I was able to do good high intensity efforts indoors. Not sure if it’s good advice, or whether it has any detrimental effects on the endurance work, but it worked for me.


I train on balcony with two fans on, and it is bloody cold sometimes, so skin cooling should not be an issue.

Thanks for the advice on the testing protocols. I pushed my TP up with a modified Ronnestad workout. Let’s see if how the 20 minutes test will go with that signature.

I hate to admit it by Zwift or any other type of racing allows me to push a bit more, just like seeing MPA dropping below the current wattage.

30s on, 15s off type workouts (I turn my brain off and focus on 30 seconds at a time) are much easier and fun compared to ramps, so mental side of it must be really important…

True. When I was using Zwift, I only enjoyed the short efforts, trying to snatch the green jersey and sometimes even the polka dot - on a (very) quiet morning :joy:

I use Fulgaz and I can get BTs using that. I have tried Zwift races before but as I generally get dropped quickly they always end up as a solo sweetspot effort.

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I get dropped often too, but at least often I bring home a BT!

Xert really is awesome. During last couple of week I recorded three activities from three different platforms. Ramp test on Trainerroad, Ronnestad on Xert and 20 min Time Trial on Zwift. Hour power is within 1-2 watt on all of them, which is 0.5% discrepancy. Of course some of them might be off, but as ensemble it looks pretty reliable.

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This was from an incremental exercise test to exhaustion in our research lab yesterday. The participant had an accurate signature on Xert, but was not allowed to look at when they were expected to fail on the test. After uploading the data to Xert, failure occured within 3s of what Xert had predicted. This image is the test with the ‘previous’ signature applied.


I would agree with you @mikhalit. I have done the standard 20’ test, the Fulgaz FTP test, seen my mftp in WKO4 and they all co-incide with my Xert numbers.
In fact I think the Xert number is most accurate as it shows decay whereas the others don’t self-adjust (mftp in WKO4 does but very, very slowly).


Thumbs up.

Just as a side comment, this is a wonderful workout to learn how failure feels like. Helped me a lot to recognize when I am choosing to stop or when continuation is simply impossible.

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Those decay/no decay calculations are fantastic!

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If you really want to learn what failure feels like, or if you’re wondering if MPA is actually a real physiological phenomenon… when you reach the point of failure during the ramp test, get out of the saddle and sprint with absolutely everything you have. You’ll likely see MPA limit your power for ~5s or so, at an intensity below task failure on the ramp test, but above your TP.

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