Since I started using Zwift, I’ve been experiencing an issue with training goals. During rest or warm-up phases (ERG mode active), the RPM and wattage targets are incompatible. For example, if I’m asked to do 55 watts at 80 RPM, my wattage meter shows a minimum of 120 watts if I aiming at the RPM goal. I’ve recalibrated the trainer (Tacx Flux S Smart) multiple times, trying to adjust my gear ratio - but the only way to successfully calibrate (45 kph) is using the big chainring and a small cog. Do I have a faulty setup?
I would guess your FTP number is set too low for your abilities if your controllable trainer isn’t giving you enough resistance in an ERG workout. Functional Threshold Power is a measurement of how much power (in watts) you can sustain for 5 minutes / 20 minutes / 60 minutes, and is a proxy for your fitness level.
If you manually adjust your FTP value by say - 20 watts - that same workout block will increase in difficulty. Instead of being asked to do 55 watts at 80 RPM, the resistance will increase at the same cadence target. Here’s how you manually adjust FTP so you can validate if your FTP is indeed too low.
There are several FTP tests available to calibrate you. All of them will ask a full effort and it’s going to be a challenge. The most fun way is new segment n Watopia called The Grade. Look for Watopia > “Elevation Evaluation” route. The mission is simple: go as hard as you can for the entire uphill route and if you set a new FTP, you’ll see what that number is as you cross under the KOM arch.
If you’re new to ERG mode workouts, it’s really important to maintain a steady cadence and just pedal at that rate even if the power is not right. You have to give the trainer a little time to adjust the resistance to match. When you’re in ERG mode, Zwift workouts may alert you to increase power, but you should ignore that. Let the trainer increase resistance while you pedal at the expected rate. Do not react to any information that tells you to increase or decrease power if you are in ERG mode.