I am using a TACX Vortex Smart trainer. I have only done 3 rides, but I have noticed that when I am doing a workout, there is no increase in resistance going uphill. My speed slows, but resistance remains the same. So basically, I am riding in the same gear for the entire workout. After the workout finishes, it seems to work correctly and increase resistance on the hills. I suspect a setting is wrong on my end. Does this have to do with the ERG mode or something else?
Hello, Keith.
We do not change resistance in workouts based on the terrain of the course. We have 2 methods for controlling resistance in workouts. The first, ERG, controls the resistance automatically to hit the target wattage - EG: If you are spinning at a constant RPM, the trainer will lower the resistance for lower wattage blocks and raise it for higher wattage blocks, to get you to the target without you altering your cadence or switching gears. The second, non-ERG, gives you a flat resistance throughout the workout, allowing you to reach the target wattage by adjusting your cadence or gear.
Not all Tacx trainers are ERG enabled - when starting a workout, if your trainer has ERG mode available, there will be an option above the ‘Workout’ button labeled ‘Use ERG mode’. If that button is unselected (or unavailable), the trainer will use a flat resistance. You can adjust the resistance once you have started the workout using the ‘+’ and ‘-’ keys on your keyboard, or using the buttons on the action screen of the Zwift Mobile Link app.
Hope this helps!
I’m in the same boat as Keith here…
I normally “just ride” and roll with the terrain and do my own workouts. However my wife really likes the idea of a structured workout plan and she’s ready to bail from Zwift because it’s “boring without resistance”. She just sits there and spins.
ERG mode seems to be enabled (I can see the option and have tried both with/without).
I don’t understand how workouts are worth doing without resistance? + & - don’t seem to do anything in workout mode either.
</2 cents>
Hey David -
Unselecting ERG mode doesn’t take away all the resistance, it just sets it at a flat rate instead of the trainer adjusting the resistance to match the target. Once you’ve started the workout without ERG enabled, if the resistance level is too high or too low, it can then be adjusted using the plus and minus keys. When you use them, you should see an orange bar on the right side of your workout HUD that shows the trainer’s resistance value. Are you seeing that bar when you use the keys?
So… I tried out some stuff with Trainerroad to make sure I was understanding how ERG is/was suppose to work.
TL;DR. My FTP score was set too low and I barely noticed the difference in resistance.
Knowing that you don’t need to change gear and that cadence plays a decent role in your resistance made me understand how to ride the workouts with ERG enabled. Oh, and to also ignore the 3D world and just focus on watts.
Thanks for the help anyways. Hopefully my ignorance helps someone else. 
Sure did thanks for the help as I was getting frustrated with Zwift
Why can’t there be an option to allow you to decide if you want to have resistance change enabled for hills when using workout mode? Why should Zwift tell how we want to workout. Can this additional toggle switch to enable resistance change on or off be added?
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I have recently started using “workout mode” after having played about in free mode with Zwift for the past 8 or so months and its taken a little bit of getting used to. I found that ERG mode didn’t feel quite right so I have been changing gear and cadence in order to hit the watt targets.
When you are using “workout mode” the assumption is that you are doing a workout in order to hit specific targets, namely watt goals in order to develop, by using a flat course its a lot easier to hit those targets in specific gears and at specific cadence, rather than having to worry about changing gear or cadence mid section because your approaching a hill.
If there was an option to allow resistance for hills you would find it would become very difficult to maintain the required targets in order to make the most of the various workout sessions.