• Mark Turnbull

Is ERG mode killing your training?

Updated: Oct 28, 2020

With the advent of the smart-trainer, indoor turbo sessions have made a massive leap into the 21st century. In addition to allowing you to capture and review performance data from your workouts, many smart trainers also offer what’s called “ERG Mode”. This mode allows workout file to dynamically control the resistance of the trainer to match a given workout profile.  All you have to do is keep pedaling.

Using my clients Functional Threshold Power (FTP), I set power targets for the workout based on their values.  Trainer resistance is automatically adjusted so you are forced to hit those targets, without changing gear.

While ERG Mode does allow the rider to just focus on the cadence, there are some situations in which good old slope or “dumb trainer “mode may be a better option.  So here are the pros and cons of ERG Mode so you can use it—or not—most effectively.


One of the biggest problems' athletes have when it comes to training is pacing themselves during an interval.  All too often riders start out an effort well above a sustainable pace. When you’re fresh it really does feel like you could hold that effort. By having a smart trainer control your effort it forces you to pace it correctly. This gives you a much better idea of how Rate of Perceived Exertion (RPE) can shift throughout a single interval, or throughout an entire workout.

For example, say you are tasked with holding roughly the same power for 15 x 60 second intervals.  When you start the set the first few intervals shouldn’t feel too hard but as you pass the 6th or 7th interval and the lactate levels build your RPE will be far higher than it was initially.  While they feel different, they should be done at the exact same effort for maximum benefit. That is where ERG mode really makes a difference. It’s far better to hit all 15 efforts at the same (barely) sustainable effort, rather than destroying yourself on the first few only to whimper and soft pedal through the last half of the workout.


Not only does ERG mode hold you accountable during the actual intervals, but it also keeps you in check during the recovery between efforts. Despite our best efforts, when riding a normal trainer or outside, the tendency is to completely back off the power as soon as you finish a hard effort. With ERG mode you still get to recover, but at a level that is more active recovery than freewheeling.

Lastly, ERG mode also helps you deliver consistent power over a given effort. Our natural tendency is to surge and ease off power at random times. With ERG mode you don’t have that option. The trainer will increase and decrease resistance in response to your output, resulting in consistent power, whether you’re pedaling at 70 rpm or 110 rpm. This allows you to complete workouts exactly as they are intended, meaning you maximise your training time.


Despite these benefits there are times when ERG mode can actually be detrimental to a given session. The most obvious is during sessions when you are trying to determine your FTP. The whole idea of doing an FTP test is to determine the absolute maximum effort you can sustain, allowing you to set your FTP for future suffering. The issue with ERG mode is that the power targets for all of the efforts in a workout based on your current FTP. The main limitation of ERG mode is this: all effort levels are based off your FTP which isn’t a fixed value. It’s a fluid, ever-moving target, one that can change from week to week and even day to day. When you’re on the bike you have your own internal RPE that tells you whether pushing 220 watts feels like a 5 out of 10 or an 11 out of 10 on any given day.

As smart as ERG is, you’re going to have days when you feel like your legs are made of balsa wood. Everyone does. Sometimes it’s because you are at the tail end of a 2-week block of structured suffering and your body is reaching its limits.  Or maybe you just didn’t eat and drink enough before entering your torture chamber.  On those days your FTP might be 5% lower than when you last did a test. What is your threshold power one day won’t necessarily be the next. That’s normal.

You have to put your ego aside and listen to your body, it knows a thing of two. Take the hint and dial back the intensity of your workout by 5% or so. If you don’t and insist on pushing it, the chances are you’ll overextend yourself, not complete the workout, and send your moral into a downward spiral, all because of a single bad session. But remember: a single bad session does not a season make. It simply means that you need to rest and recover as enthusiastically as you train.

The opposite can also be true. After several weeks of good, consistent training, and proper rest, your FTP might have gone up 5%. Unless you update your FTP setting, your smart trainer would have no idea. You might end up breezing through a workout that was supposed to be much harder. 

Apart from FTP tests, I always suggest to clients that there are other sessions that simply aren't suited to completing in ERG mode. These short, rapid fire, on/off efforts are best done in slope mode, so you can unleash your high speed and power for each effort (without waiting for the resistance to ramp up).

With ERG Mode, there is nowhere to hide. There is no try, there is only DO.

ERG mode is a very useful tool that has its purpose. Pacing, accountability, consistency—all of these are made easier by ERG mode. But tools are only as good as the craftsman who uses them. When it comes to establishing baseline metrics like FTP, or when your body is telling you something different, let your smart trainer play dumb and get reacquainted with your shifters and use your RPE.

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