Power v. Cadence v. Speed inconsistent (Zwift Hub pairing issue?)

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1

I did my very first SMART workout today. It was fun esp while getting to watch Le Tour!

My setup is with a Zwift Hub and running the Xert app on my iPhone. Everything seemed to pair up and work fine until I got to the second set of intervals where power cadence and speed seemed to decouple during the rest periods between two intervals outputs. I am using a Zwift Hub with the latest firmware.

If it helps I shared my activity results here: Xert - Activity | SMART - Say It Ain't So - 45

Note the rest periods between the 26 and 32 minute marks. I’ll do a more structured test next workout to make sure I am in the same gear the during those rest periods as that is one variable I can’t account for (I am fairly certain I was in my top gear or near top gear throughout which is like a 52:11).

I wonder if it has something to do with how I paired to my hub? I see when I pair from the Xert app in settings that there are a few options:

Power Source has:
Zwift Hub FTMS (Trainer) ← I selected this one
Zwift Hub (Powermeter)

Trainer Control has only one:
Zwift Hub FTMS (Trainer) ← I selected this one (obv)

Cadence has:
Zwift Hub (Cadence Sensor) ← I selected this one
Zwift Hub (Powermeter)

Speed has:
Zwift Hub FTMS (Trainer) ← I select this one
Speed from GPS
Speed from Power
Zwift Hub (Cadence Sensor)
Zwift Hub (Powermeter)

If there are any other details that would help or some resource to look at just let me know!

Best,

Sean

2

Not sure of the best setup for a Zwift Hub but I would think these are the settings you want to use.
Power Source: Zwift Hub (Powermeter)
Trainer Control: Zwift Hub FTMS (Trainer)
Cadence: Zwift Hub (Cadence Sensor)
Speed: Speed from Power

For workouts under ERG control many prefer the small ring with a mid-cog to provide the best chain line (least friction/noise). However, flywheel speed is a factor so use whatever gear combo feels best with your trainer.
SMART workouts encompass a range of interval options not anchored on %FTP. You’ll also encounter Mixed Mode intervals where trainer control will switch from ERG control to Slope mode and you’ll use gears/cadence to match targets.

3

Thanks for the reply! I’ll try those settings in the morning as well as check out if I am in ERG mode or not.

Cheers!

4

Xert player apps default to AUTO mode which switches between ERG control and Slope when appropriate.
MIXEDMODE is typically mentioned at the end of the workout description.
If you view Workout Details you’ll notice some intervals are defined with a % grade.
Common usage would be for sprint intervals where the goal is max efforts rather than fixed watt targets. Other times the intent is to simulate riding outdoors.
Examples:
SMART - Adventure of a Lifetime - 60
VIRTUAL - Ellis
SMART - Asking For It

5

Those settings (and choosing a single gear) seemed to work great. Me going from 85 watts to 450+ watts in less than 10 seconds was less awesome. ;).

Maybe next year!

Best,

Sean

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