FTP test was bonkers - had to peddle at 120rpm cadence. Whatsup?

Hi everyone, I have been Zwifting for about a month and this is my first post on the forum. Health and happiness to everyone.

I did an FTP test a month ago, start of November. Been a cyclist for about 25 years. But first time I have ever done indoor cycling training after I got my Wahoo Kickr. I love it with Zwift. I had a reasonable amount of base fitness and I did the FTP test - ramp test; first thing I ever did on Zwift. 285 Watts. Cool.

Been Zwifting five times per week and making solid progress on all hills/sprints etc. Cool. Gosh it can be hard! :slight_smile:

Today I did another FTP test after a month of solid progress that I have really enjoyed, especially in the dark, cold, windy UK when otherwise there’d be no opportunity for cycling.

ERG mode on. Ramp test as before. Innsbruck. I could not do 50W on the course since I could not peddle at the cadence required to do 50W. Even at 50W it was saying “more power”. All the way up to 240W I was peddling at an insane cadence to try and match the power that was being asked for. I was in my big ring and smallest sprocket on the back. 130rpm. And after all that peddling my FTP had gone down to 190! This is nuts and not right. I can hold 270-300 for almost any course with ease. Immediatly after the FTP test I did the Royal Pump Harrogate course and Zwift corrected my FTP to 250Watts.

Any thoughts what I am doing wrong please on the FTP test?

Happy holidays, Steve

In ERG you should be in the small ring and in the middle of the cassette.
If the flywheel speed of the trainer is too high, the trainer can’t brake it down so you can reach your watts.

More Power doesn’t mean higher cadence. In ERG this means, the trainer have to give more braking power.

Hi Ben, but surely that would mean I’d be peddaling at an even higher cadence - unsustainably high?

And the faster you pedal, the more the trainer will reduce resistance to try and make the power target. So you get into a vicious circle. A bit like the death spiral if you pedal too slowly and it keeps increasing resistance.

Please inform yourself, what ERG is and how it works.
Sorry, my english is too bad to explain this to you.
I bet there are far better explanations out there than I can give.

OK guys, clearly I am doing something wrong. Never had that issue on the first FTP though. I will read into ERG mode further as suggested.
Many thanks, Steve

ERG mode can feel very counter-intuitive at first. When the trainer is telling you to pedal at a particular power level, it adjusts the resistance to your cadence, so that you produce the correct power.

The counter-intuitive bit is that the faster you pedal, the less resistance you’ll feel (opposite to normal cycling), because more rpm needs less resistance to produce the correct power. And the slower you pedal, the greater resistance.

So to allow it to work, you need to hold a relatively steady cadence. Depending on your trainer model there might be a slight delay as it adjusts the resistance.

So if you keep pedalling faster and faster, the trainer will keep reducing resistance and you’ll end up with the scenario that you describe.

Use the small ring, middle of the cassette, settle on a cadence and give the trainer a few seconds to adjust resistance, and it should work.

Did you get this sorted Steve? On one or two occasions my Tacx flow has not connected properly to the app resulting in low power readings (and requiring high cadence to reach specific power levels). The issue I had was an old laptop with dodgy Bluetooth connectivity. I switched to using an iPad and haven’t had the problem again since.

Hello Mark,
Yes. I use an Apple TV 4k. As suggested by Steve I did as follows:
“Use the small ring, middle of the cassette, settle on a cadence and give the trainer a few seconds to adjust resistance, and it should work”. It’s all about setting off very modestly at the beginning so the system can set the initial resistance. At the end of the FTP test the trainer ramped it up such that there was so much resistance I was pedalling squares.

I did a 348 FTP test which I have very pleased with :slight_smile:

Hi, sorry to hijack the thread but I it also true with a MTB where the rings and cassette are differents compare to a road bike?

I used to do my workout with the big / medium ring and the small ring on the cassette.

My problem is that with a MTB it looks harder to get to 90-100rpm or you have to go crazy fast with your legs.

If you’re just doing ERG, you can use a MTB. It makes no difference. The trainer controls the resistance.
If you want to do SIM, get yourself a road bike, or a very big chain ring on your MTB.

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Thank you.