Power measurement on cyclops fluid trainer

I have been performing 2x20 intervals on a Cyclops fluid trainer using the powertap SL system. However, I notice a significant variability in average power when comparing the two intervals. When performing the two intervals my speed, cadence and gearing are identical yet average power drops by 10% during the second interval. Consequently, in order to reach the same average power during the second interval, I must increase speed and/or cadence and my perceived exertion also increases. Is this an intrinsic problem with the Cyclops trainer itself? Has anyone else noticed this type of problem with other trainers?

Variability is inherent in almost all trainers because temperature affects the amount of resistance provided. If you have power data available, pace your intervals from that and ignore speed/cadence.

This is what I have been doing. I suppose if resistance is dropping during the workout this would make sense. However, I feel that I am working harder during the second interval in order to attain the same power level. It also becomes dificult to guage longterm improvements if there is variability in resistance levels

I agree with frenchyge, many trainers have issues with resistance changing as they warm up. Everything points to the resistance dropping on yours as you ride it. As to why the RPE increases on the second effort, two thoughts come to mind.

- It's the second effort and you're feeling the effects of the first. I know my 2nd twenty minute L4 effort often feels tougher than the first.

- You're staying in the same gear and increasing cadence to increase wheel speed. It's pretty common for RPE to increase for the same power output at higher cadences. Have you tried bumping up a gear or two and keeping your cadence the same or even dropping it relative to your first interval?

Good luck,
-Dave

London, I have a Fluid2, but my experience seems to be the opposite of yours, i.e. the resistance goes up as you ride an interval. I actually used to pace my efforts with a speedometer. I would hold the same speed and, boy, it sure got harder towards the end.

That all changed when I got a Powertap. The first few times on the trainer, I kept the speedometer on and just rode the intervals as I had done before, and the difference in resistance was pretty big.

Here's a picture of an interval where I held power in the 280s. As you can see, the speed keeps going down as I went on (which is because of the increase in resistance).



From what I've read, there's an exceptional amount of variability in the Fluid2 resistance units. (Some units have more resistance than others...some gain resistance...some lose resistance, etc.) I heard they have worked on minimizing that with the new line of trainers though....

But as the others have said, the watts are what really matters. And yes, it's usually harder to hold your power on the second interval. Sometimes you really have to dig deep.