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ERG Mode for Indoor Cycling Explained: What You Need to Know

calendar icon January 11, 2025
calendar icon 6 MINS
author icon matthewmace

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Everything you need to know about ERG mode for indoor cycling.

ERG level mode RCA

If you’ve traded bib shorts and suntans for a smart trainer this winter, you’ve likely asked yourself the following: What is ERG mode and should I use it? 

This article explains everything you need to know to help you increase cycling fitness and skill development, even on the smart trainer.

In this article, we cover:

  • What ERG mode is
  • The benefits and drawbacks
  • When and how to use it 
  • Why free riding (level mode) is a good alternative (and how to use it)

Would you rather listen to coaches Cam and Ryan talk about ERG mode for indoor cycling? Listen to the podcast episode below.

What is ERG mode?

Ergometer mode, known as ERG mode, is a feature on most smart trainers that automatically adjusts the resistance to meet your prescribed power target.

When using ERG mode, the trainer does the work. You do not need to shift gears; you just need to maintain cadence to control your effort (watts). This helps ensure you stick to the power demands of your workout.

For example, if your prescribed plan requires 3×10 minutes at zone 3, you would set the power (w) to 80-90% of your threshold. If your FTP was 250, you would set the trainer to approximately 200 to 225w. 

What are the benefits of using ERG mode for indoor cycling?

There are a few benefits of using ERG mode for indoor cycling. We discuss these below.

Consistency in power output 

ERG mode locks you into a target power, helping you ride at a given effort without changing gears or making adjustments on the fly.

This ensures you stay in the correct training zone when riding to eliminate excess fatigue and zone overlapping (e.g., accidentally accumulating time in zones 3 or 4 when you should be in zone 2). 

You can focus on pedalling  

With the resistance set by the trainer, you only need to focus on maintaining cadence during your ride.

When using a program such as Zwift, your power output remains steady, even when riding up or downhill. You also do not need to shift gears, making your workout less technical and easier. 

All you need to do is focus on pedalling to maintain the power output. If you can’t sustain a mid-high cadence, problems begin to appear—but more on that shortly.

ERG mode is great for Zone 2 and Sweet Spot work

Workouts where consistent power is critical, such as Zone 2 or sweet spot sessions, are ideal for ERG mode.

You can maintain consistent power without unnecessary spikes in effort, such as riding up or downhill. You simply set the target power and ride.

Furthermore, because zone 2 workouts are often more tedious—there’s less to focus on—you prevent zone overlapping where previously you might have zoned out and entered zone 3, for example.

See the below image for an example of how ERG mode works in Zwift.

Zwift indoor training example

Useful for tracking progress

When you lock the power (w), you can track your progress over time using a couple of simple measurements, including:

  • Cadence—do you notice an increase in average cadence?
  • Heart rate—do you notice a decrease in your average heart rate?

If the above measurements improve, this is a good sign that you should increase your target power so your training zones best reflect your current fitness.

What are the downsides of ERG mode?

Although the benefits are plentiful, there are also a few downsides to consider before using ERG mode.

The “Spiral of Death”

If you’ve ever done a ramp FTP test, you’re likely familiar with the “Spiral of Death”—this is when your cadence drops too low, and you can no longer sustain the target power. This quickly makes pedalling impossible and causes you to fail the workout.

The Spiral of Death can also occur in other high-intensity cycling sessions, such as VO2 max efforts. When you can no longer maintain a mid-high cadence, you would need to either turn ERG mode off and manually ride within your target power zone or reduce the FTP percentage to the lower end of the zone.

ERG mode is restrictive 

Although one of the greatest benefits of ERG mode is the restrictive nature, i.e., you’re locked into a prescribed power, it’s also one of the main downsides.

The restrictive nature of ERG mode means you can’t push harder when you feel good.

From a coaching perspective, pushing more watts on those sessions where you feel good is a great indicator of progress and allows you to be more intuitive with your training and body.

Because ERG mode locks you into a given wattage, you can’t adjust—other than minute increments—mid-ride. For example, if doing a VO2 effort (approx 106-120% FTP), ERG mode locks you in at around 113%. This intensity may be too high on a given day, but you might have been able to perform the session at 106%.

Having the ability to adjust your power output in these high FTP sessions can often mean the difference between a successful workout and having to abandon your session.

The below image shows free riding on Zwift—there is no set power to maintain.

Free ride Zwift example

Limited skill development 

If you constantly use ERG mode, you will struggle to develop real-world cycling skills such as maintaining power over various terrains and gradients and effectively shifting gears.

Even if you plan on racing on Zwift, these races are in level mode. You can’t set a power and let the trainer do the work for you. You have to work for it!

By adding free riding into your indoor riding, you will also develop the skill of applying constant pressure to the cranks. This has become somewhat of a motto here at the RCA.

How to use ERG and level mode for indoor cycling

Any good cycling program that contains indoor riding should use both ERG and level mode.

If you currently only use ERG mode, add 1-2 rides in level mode for added flexibility and to develop key cycling skills. Try switching out those high-intensity sessions, such as VO2 or other high-intensity sessions, for the free-riding alternative.

Try not to get frustrated if you see power fluctuations when switching to level mode. This is completely normal—you will get stronger by including variability in your training, which also helps skill development. Moreover, it’s normal for your power to fluctuate daily so don’t stress it. 

If you want a little extra guidance, RCA Head Coach, Ryan Thomas, has put together 4 and 12-week indoor cycling plans that include ERG and level mode sessions.

Key takeaways

  • ERG mode locks you into a set power (watts)
  • It’s best for sustained efforts to prevent zone overlapping
  • Rides done in ERG mode allow you to track progress (increased cadence and decreased HR)
  • When using ERG mode for high-intensity workouts, you risk failing the session because you can no longer maintain a high enough cadence to sustain a given wattage
  • Add 1-2 free rides (known as level mode) for high-intensity sessions for a more intuitive approach to workouts with less risk of failing  

FAQs

What does ERG mode stand for?

ERG mode stands for ergometer mode. It’s a useful setting on most smart trainers that allows you to match a prescribed power output, regardless of what gear or terrain you’re riding.

Why is ERG mode so hard?

ERG mode can be challenging at high intensities because it locks you into a given power. If you can’t sustain the number of watts, you fail.

When should I use ERG mode?

ERG mode is best used for zone 2 rides or long sustained efforts, including sweet spot rides.

Should ERG mode be on for an FTP test?

We recommend not using ERG mode for your FTP test. You do not want the trainer to restrict your maximum effort and FTP.

How to turn on ERG mode on Zwift?

To turn ERG mode on, toggle the “use ERG mode” button when choosing your ride or workout.

How to turn off ERG mode on Zwift?

To turn ERG mode off, toggle the “use ERG mode” button to off when choosing your ride or workout.