Spin Faster - Reduce power

im using a tacx flux smart trainer which is connected via blue tooth to my phone and use my Apple Watch as my heart monitor.

I am fairly new to this and have just started using the Training modules in erg mode. I am having trouble with the low watt part of the rides, as it keeps telling me to reduce my power but spin faster. If I spin faster, my watts increase, if I reduce power my rpm slows down and I get the message to spin faster so I can’t win.

I must be doing something wrong but can’t work out what. My gearing/chain is in the middle of the ring but as I understand this shouldn’t make a difference.

It also seems to take a long time to calibrate my spin speed, I have it on 3 second average power measure.

Any advice out there? Would this solve the issue?


You are sort of correct with you don’t need to change gears, however it does make a difference in the case of low power/high cadence. I find I need to change gears with my Flux when doing low power high cadence workouts. What works for me is I use small chain ring on the front and change up and down the rear cassette. I guess it also does depend on the type of workouts you are doing and the power you are trying to maintain.


Ah one more thing I always use the Tacx app to calibrated my Flux not the one in Zwift.

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How does it work?

This graph shows an ergo-training for the FLUX Smart with a certain gear setting (39 tooth front chainring and a 19 tooth rear cassette). It illustrates the amount of wattage (power level) that the Tacx FLUX Smart can produce in the specified gear setting with a certain cadence. The blue shape represents the available resistance levels of the FLUX Smart. For example, at a cadence of 75 RPM, the FLUX Smart can power up to 400 watts in the 39-19 gear setting. This trainer cannot produce power levels below or above this shape, in this gear setting. If you wish to do so, you have to shift your gears. For example, at a cadence of 75 RPM you have an output of 100W. If you wish to ride with a lower wattage, you need to change gears; between 21 and 28 tooth.

Please note, using another gear setting will change the starting point; the lowest and highest possible power level at 0 RPM. This way you can determine what the best gear setting should be for your training.

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