If you do a workout with a smart trainer, you may have the option to use ERG mode. ERG mode is available on select smart trainers and sets the resistance to a specific wattage target based on your cadence instead of basing it on the course gradient (SIM mode).
What's this mean?
As an example, let's pretend you're going into a workout interval with a target of 150w. Here are the key differences:
- The resistance will change based on your wattage target and cadence: If you're going at 60 RPM (revolutions per minute), the resistance is going to ramp up so that your 60 RPM generate 150w. Alternatively, if you spin up your cadence to 90 RPM, you'll feel the resistance drop so that you're still putting out 150w. It may take your trainer time to adjust, so it's best to spin at a consistent cadence or slowly change your RPM.
- No shifting: Since your trainer is automatically adjusting your resistance based on your cadence/wattage target, you don't need shift your gears. Get into a neutral gearing for your chain and pedal away!
- Wattage target vs course gradient: When you're going up or down a hill, you won't feel the resistance change based on the gradient, only the wattage target. Your speed in Zwift will still be calculated based on your wattage, and in that sense, it's like riding a classic trainer.
In summary, ERG mode is only available in workouts, just like SIM mode is only available in free ride. In ERG mode, resistance doesn't change with the course - it changes with wattage targets.
How to use ERG mode
- If ERG mode is available on your smart trainer, you'll see a checkbox with the "Use ERG mode option" on the workout selection screen. Click the box.
- Pick your workout and join the world.
- Get your bike into a gear that'll reduce wear on your chain/keep it straight.
- Start pedaling at a cadence you're comfortable with. Just be careful if you have high wattage targets on your workout - you might need to kick up your RPM!
A Note on Gearing // Avoiding the Resistance Floor
Depending on your trainer, you may need to adjust your gearing (from your big ring to your little ring) to hit your wattage targets: if your power target is below the wattage at which your trainer can apply resistance, you hit the "resistance floor" (also referred to as the “wattage" or "power" floor) and you won't feel resistance changes.
The resistance floor varies from trainer to trainer, so we can't tell you if you're going to hit this based on your workout or FTP, unfortunately. An easy way to identify it is if you notice your power isn’t being held down to the power target. In this case, change into that easier gearing ratio to try and reduce the amount of resistance needed to bring your power down.
In short, if you don't see your power decreasing while using ERG mode, try a smaller gear ratio.
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