the thing that bothers me about erg mode is that it promotes unnatural behavior (for me):
- Erg mode rewards constant cadence, something I don’t do find myself doing very often on a mtn bike
- Erg isn’t too happy with low-cadence work (40-60rpm) and I have to switch to standard/level or resistance mode to do torquey tempo work
- Erg rewards me for spinning faster (100+rpm) on short on/off and vo2max efforts, whereas outside I do those intervals with a little more torque at 80-90rpm
On the other hand Erg mode is pretty sweet on long SS workouts, or forcing me to stay in zone1 on recovery rides, or zone2 for aerobic endurance work.
Erg is just one of several tools you have available with a smart trainer.