Originally Posted by
WhyFi
Eh, it's just that the idea of it doesn't appeal to me. Ride simulation isn't something that interests me, so I see ERG mode to be the most compelling aspect of smart trainers... but that just seems wrong to me, too. Without shifting, I expect my power to go up and down respectively, with the increase or decrease of my cadence, but ERG mode ain't having that.
You will get some power variation in ERG mode. Those pure geometric profiles you see on Strava are usually because the trainer is sending target power, not actual power. You can certainly change cadence or shift gears during ERG mode and system will settle back to the ERG target. I usually see a ±5-7 watt change in actual power depending on how smooth I'm pedaling. Plus you could shift gears to change intensities as the interval changes. Going from recovery to VO2 is a shift change. You could keep the same gear, but you then rely on the trainer to evaluate power and adjust. It's not as instant as shifting.
What is weird is that it's a double feedback system, your pedal force and cadence trying to maintain a power and the trainer trying to stay within a power band. I generally find it easier to do intervals in ERG mode than following terrain as I can focus on the power and not worry about little descents or risers. But the terrain simulation is also a benefit as climbing means actually increasing power as one would do outdoors too.