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Ergometer mode, or ERG mode as it is more commonly known, is a function of most modern smart trainers which allows the trainer to set the resistance for you. If your target is 200W and you go above this, the trainer will reduce the resistance to stop you from going any higher. If your wattage drops below the target it will increase the resistance to encourage you to put more force through the pedals and get back up to target.

To many cyclists this sounds ideal. It allows them to relax for a bit and watch some TV while they train or listen to an audiobook. Safe in the knowledge that their trainer won’t let their power drift too high or too low. However, it’s not without its problems, which I’ll go into here.

Riding in a vacuum

When riding in ERG mode you don’t have to think about gradients and changing gear. However as your target event is probably outside, this does not prepare you for the realities of racing a bike outdoors. Make sure you do your steady state rides outside of training mode on a virtual course to prepare you for this. This is especially important in the last eight weeks before your event.

The Spiral of Death

An athlete getting caught in the spiral of death, unable to get their cadence high enough to reduce the resistance, resulting in the workout being abandoned.

If your cadence drops significantly or you stop pedalling ERG mode will instigate what many call the spiral of death. This is when it increases resistance dramatically as you’re not putting out enough power. If you’re in the middle of a tough interval, this can feel like riding through wet cementas you try to pick the pace up again. We all drop our chain, have to answer the door or adjust the fan sometimes, so this is something to be conscious of. You may end up having to skip an interval or even abandon the workout as a result.

Problems with Power Meters

If you own a power meter you should be using it for all your training to make sure all the numbers match. This helps to keep your data clean and ensure all your intervals are accurate. There is something of a problem however as the training software will listen to the power meter, check the power output against the target, and then tell the trainer to increase or decrease the resistance. When the device creating the resistance isn’t the same as the device measuring the power, the ERG mode isn’t nearly as accurate or immediate to change reistance. This means you need to focus much more on holding targets, offering the worst of both worlds.

For harder workouts this can be beneficial if you feel you would struggle to complete it otherwise. However I find that more often than not it’s more effort than it’s worth.

Inability to change gear

You can physically change gear in ERG mode, but the trainer will pick up on this pretty instantly and change resistance. If you find yourself pedalling squares desperate to increase you cadence, the only way to do this is by pedalling harder to lower the resistance. If you’re really struggling in a workout however, your ability to hold this cadence may be compromised. This will likely result in your cadence slowing again and ERG mode “carrying” you through the rest of the interval at 40RPM. There is a time and place for this, such as a ramp test, but you can’t get through every hard interval this way. Disabling ERG mode will give you a more authentic training experience.

Lazy Cadence

The inverse relationship between power and cadence in ERG mode as intensity increases (power in purple, cadence in yellow)

Perhaps the biggest issue I have with ERG mode is the way it encourages a slow, lazy cadence. Riders who start to fatigue will naturally slow their cadence, yet ERG will push back to ensure they stay within the power target. This can result in riders associating harder efforts with a slower cadence and ultimately spending most of their time in tempo and sweetspot at 70RPM, well below where I’d want to see athletes riding, even the low cadence advocates will race at 80-85RPM. You can’t afford to spend time fiddling with your gears trying to find the narrow cadence window you’re used to riding in from training.

Uneven wear on cassette

If you do a lot of riding in ERG mode, you will be doing a lot of riding with minimal (if any) changing of gear, which can create a lot of uneven wear on the cassette, wearing one or two cogs excessively which will lead to shifting issues.

The subject of which gear to ride ERG mode in is also continuous in itself, this video from GPlama explains it well: https://www.youtube.com/watch?v=uHUOhmG04M8

I’ve given ERG mode a bit of a bad rep so far, but there are some definite benefits to using it.

No need to concentrate

If I have to use the turbo for my steady state rides, I’m happy with the entertainment provided by the scenery and the changing gradient, but that’s me, and I know not everyone is as easily entertained. For many, turbo training is the perfect time to catch up on the latest Netflix series or watch a film their partner isn’t interested in. With a pair of bluetooth headphones they can enjoy some televisual entertainment while riding, and ERG mode keeping them within the power boundaries. This is more useful for steady state workouts than intervals, as most software does not integrate with video, so you may end up being caught unawares by a sudden increase in resistance.

Helps you complete tough workouts

The mental element of training is just as important as the physical element of training, and for many the presence of ERG mode is the difference between them completing or failing a workout. I’d much rather someone limps over the line and completes a workout at a low cadence than they have to give up and bail twenty minutes in because they can’t hold the power without their trainer pushing back. This provides a safety net for many cyclists, and as long as they’re conscious of the shortcomings of ERG mode (not to let cadence drop too low, don’t stop pedalling, e.t.c.) then they should do whatever it takes to complete the workout.

Conclusion

So, should you ride with ERG mode? As ever… it depends. For workouts which include lots of micro bursts or short sharp increases in intensity such as V02 or sprints, absolutely not. If it’s an easier workout where you’re more concerned about going too hard than too easy and want to watch Breaking Bad while you do so, then it’s a good choice.

The difficulty comes with the middle ground, the tempo and sweetspot rides where riders may find comfort in the knowledge ERG mode will help them complete the workout. For this, I would look at how close to race day you are, if you’re six weeks out from your A race, then switch it off and learn how to control the intensity yourself. If you’re nine months away from your next big event and just doing some base training, then do whatever it takes to get you through the session.

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