1. ERG Mode (Ergometer Mode)
- What it does: In ERG mode, the trainer automatically adjusts the resistance to maintain a specific power output (measured in watts) regardless of your cadence (pedal speed).
- How it works: If your training plan calls for, say, 200 watts, the trainer will keep the resistance steady so that you’re always generating 200 watts. If you pedal faster, the resistance will decrease, and if you pedal slower, the resistance will increase to keep you at the target power.
2. SIM Mode (Simulation Mode)
- What it does: SIM mode simulates outdoor riding by adjusting resistance based on factors like gradient (hill incline), wind speed, and even road surface (if the trainer and app support it).
- How it works: The trainer dynamically changes resistance to mimic real-world terrain. If you’re climbing a virtual hill in an app like Zwift, the trainer will increase resistance to make it feel like you’re actually climbing. When you go downhill, it reduces resistance, mimicking coasting.
Conclusion: If your trainer/Rouvy setup changes resistance when approaching a virtual gradient, you are not in erg mode in the first place.