Your trainer probably cannot create high enough resistance at low rpm to hit 400w. Only the most stout trainers are capable of the very high resistance you probably need.

It is because you are shooting for a number that is too high for you (at least right now).
You your power starts dropping, then the trainer tries to adjust to keep you at 400, so cadence gets harder to maintain, repeat, repeat, repeat down to 10 rpm.
Smart trainers go into the "cadence death spiral" when you are not holding the number that you set.

If you set 400- and kept holding 400 at 90 rpm or better there would not be an issue. In fact if you try to boost power by a measurable amount it will keep adjusting and cadence will increase.

The way trainer control works, your cadence drops, your power drops, your trainer increases resistance. You were working at an unsustainable power, so the actual power you output was dropping continuously for the last 30 seconds following that cycle. Plus if you're moving at 10 rpm at the end, I highly doubt you were actually putting out 400W at that point. Long story short, it doesn't count as 400 W because you werent putting out 400 W. As soon as the cadence starts dropping, your power will have as well.

I'd question why you're trying to do intervals like that in erg mode.

Why? We do lots of trainerroad erg workouts that have us doing intervals like that. Though if it has us to the point of almost grinding to a halt, then could be a sign we have our ftp set too high.

400w is 400w no matter the cadence no?

or at 10 rpm i am putting out more torque than watts?




ramp test

exxviii said, at that low of a speed the trainer isn't capable of producing enough resistance to do 400W. DCR just mentioned something similar in his Tacx Flux 2 review.

As other have hinted at. I would not try intervals below like 50 rpms at higher wattages. Trainers simply are not engineered for the torque created at a really low cadence. Also, I'm not sure what value doing such low cadence training will do for you. If you are trying for weight training, then just go to leg presses and squats. Trainers are better used for aerobic fitness.

i guess it applies more for hill climbing. i like to stand up and mash the big gears while others sit and spin granny gear. but i guess changing my style of training knowing this via the trainer can only make me better

Maybe back into it by forgetting the number and ask if you have a training goal related to riding 10 rpm, if not then adjust the duration or load to keep the revs up. Or just do the same workout in non erg and see what the number look like

i am sure we all hit that one hill where we run out of gearing and have to do that... unless you live somewhere flat.

 



ramp test[/quote]
In that case its not an interval per se.

This is one of the problems with ramp tests imo in trying to determine ftp, people aren't willing to take an ego hit, and the likes of TR and Zwift want people to see bigger numbers.

The idea of the test is to go until you can't hold it STEADILY. If your cadence has dropped by more than about 4 or 5 rpm over the last couple of steps, then you are done. That's why its saying you haven't averaged whatever power it was meant to be.
In your case, I'd say you are probably 2 steps lower than that as a finish point.

Now if you were doing it as a straight out minute interval, my initial post remains.
Do them out of erg mode; Its quite possible being able to change gear a little to keep on top of cadence and you might be able to complete the intervals rather than getting your leg humped to death by the trainer equivalent of a jack russell.
It also gives you the feel of what those intensities feel like, unless you always ride on whats essentially a 15% gradient in 54/12 to hit those numbers.

In that case its not an interval per se.

This is one of the problems with ramp tests imo in trying to determine ftp, people aren't willing to take an ego hit, and the likes of TR and Zwift want people to see bigger numbers.

The idea of the test is to go until you can't hold it STEADILY. If your cadence has dropped by more than about 4 or 5 rpm over the last couple of steps, then you are done. That's why its saying you haven't averaged whatever power it was meant to be.
In your case, I'd say you are probably 2 steps lower than that as a finish point.

Now if you were doing it as a straight out minute interval, my initial post remains.
Do them out of erg mode; Its quite possible being able to change gear a little to keep on top of cadence and you might be able to complete the intervals rather than getting your leg humped to death by the trainer equivalent of a jack russell.
It also gives you the feel of what those intensities feel like, unless you always ride on whats essentially a 15% gradient in 54/12 to hit those numbers.[/quote]
i have also done it in interval training. training programs like zwift not really based on your ftp, at least im glad you can hit page up/down to adjust the interval.