Doubts about my ftp test

Hello,
Sorry if it has been asked before, I’m pretty new to training indoor.

So I did my first FTP test one hour ago and I have a couple of questions. I had calibrated my trainer (a very basic one, tacx flow), with the the chain on the small chainring and middle of the cassette.

But what I noticed is my cadence was rather high during the test and at some point my power target was like 200 and my cadence 120+ (although it might be overestimated as I don’t have a dedicated cadence meter).

So I just moved the chain on the big chainring and it was much more confortable… I could continue the test for some more minutes but I was a little bit disturbed: isn’t the whole point of ERG mode the adaptative resistance FROM the trainer? I would have thought I wouldn’t have to change my gear… So I suspect something is wrong with my setup / how I did the test. Do I need to do the test with a specific average cadence? Which one? Do I need to calibrate the trainer so that when I’m starting the test, the cadence is not too high?

Here is a screen capture of the test (I don’t know if I can directly share the link)

You can notice the change of gear at some point after the cursor.

In any case, I was pretty exhausted at the end of the test.

Many trainers have ceilings and floors in how they handle power particularly on the low end of power since most can support power above what almost everyone can handle. Seeing your FTP at 156, it’s likely that your trainer was struggling with such a small gearing at the lower power targets. Running in the big ring likely put the trainer within the range it’s more capable in. So the answer is specific to both the trainer, your power, and the gearing you were using. Generally speaking the answer is no, you don’t need to test at a specific cadence, but you do need to know what your trainers limits are and shift gears during the test accordingly. If the big ring works throughout the test, I would just park it there.

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I think you were subconsciously pedaling faster to increase your power at each step, and your trainer responded by lowering the resistance to bring the power back into range. Changing to the big chain ring then increased the resistance. You can see that you increased your cadence in the step immediately after your chain ring change.

I am not the best ramp test taker, but I think you generally want to hold a fairly consistent, comfortable cadence through the test. I would probably shoot for what works well for you at threshold efforts and then try to increase gradually as the power reaches your VO2 max levels.

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Yup, cadence creep is a real issue sometimes. I think people see the power step and increase cadence in a natural response. But you really need to watch and maintain a cadence as best as possible. Increasing can lead to these issues.

There are legit needs to shift with some trainers, and this is likely one of those examples, but the cadence creep here made it a bit messier.

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I felt that I had to spin really fast to meet the power target. So, had I choose to spin slower, the resistance would have adjusted?

Yes, with this trainer, assuming you are in ERG mode, it is supposed to increase or decrease resistance to match the desired power target. Notably, this is a low cost unit, and will hit limits where it won’t be able to reach some high or low powers, depending on which gear you use. So some shifting may well be necessary.

But generally speaking, for ERG, you pick your desired cadence and let the trainer and controlling app make the necessary adjustments.

If you are new to ERG, this is a great video to watch.

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This guy has class. Listen to his advice.

Even the high end trainers have limitations. You’d probably do the same thing on a top end unit.

You have a inexpensive “smart” trainer. This type of trainer can only provide so much resistance so you will need to shift to bigger gears to get more power.

I have a Smart Vortex. I’ll warn you that these trainers can be not so accurate. So, don’t get too married to the number it tells you. Some day, you may get a real power meter and lose 50 watts from your FTP.

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whatever your self-selected cadence is.

… or gain … but most likely lose

Yep, it’s just the basis for training on that trainer without any other data points to latch on to.

Use what you get for now, and if your equipment changes you will have to do another test.

Also, in general, don’t get too married to the number at all. It goes up and down daily, under normal circumstances.

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