Week 6 Gran Fondo training plan, terrain ride workout.
It has a large free ride block in the middle of the workout. The workout description says to pick a tough route because it will use the “natural” terrain. There is no change in resistance going uphill. It’s just like pedaling on flat all the time. I’ve tried cycling ERG on/off on my phone but it didn’t change anything.
Free ride blocks don’t normally use the terrain, so you feel no gradient.
Either that descriptive text is wrong/misleading, or the free ride block hasn’t been configured to use the gradient (I think that’s an option?).
I’m not exactly sure what the workout description is referring to, and perhaps this is either incorrect or misleading information. I know there are perhaps some slightly different terrains or road surfaces in Zwift (e.g. cobblestone VS regular paved road), but the only way (as far as I’m aware) that one can “feel” these different surfaces is if one has a Tacx Neo trainer with the road feel settings enabled.
So, what Steve said is absolutely correct. It doesn’t matter what course or route you chose in this instance; if it’s a free ride block in an ERG mode workout, your trainer will be “free”, which means the only resistance you will feel will be the physical weight of the device spinning with no added resistance from your trainer. Free ride blocks are intended in workouts to be a flat (0% gradient) for the duration of the segment. It may be possible to change this as an option, but I’ve yet to find anything explaining about that.
This is also somewhat mentioned in the Wattage target vs course gradient section of the ERG mode article.
You can change the resistance using the ± buttons on the KB or the incline buttons on the Companion app.
or you can use the FlatRoad=“0” to modify the workout.
Thanks Gerrie.
I know for a fact that I knew about this previously, but must have forgotten. Since you effectively called me out, I’m sure my brain will retain this piece of information from here on out! LOL 
Sorry didn’t mean to call you out, I just wanted to add some information.
Years of not having ERG made me very capable of using the incline buttons.
Not a lot of people know about the Flatroad edit. (I have to google it every time I want to use it).
No worries, Gerrie, and I’m definitely not offended. I do my best to retain Zwift knowledge and information, but occasionally things will slip my mind. Plus, my brain is having an off day somewhat today too, which doesn’t help. Either way, I don’t pretend to know everything about Zwift, but I do my best to retain information as best I can.
As always, your knowledge, insight, and experience is much appreciated, and I thank you for sharing it.