What is ERG mode?

ERG mode is a setting that certain smart trainers have, such as the Wahoo KICKR and Tacx NEO.  It effectively allows you to hold a specific power output and therefore train in a very focused way targeting a particular energy system. 

It’s an absolutely fantastic tool that can simplify your training and really hone in on a specific area you are looking to develop.  For instance, if you want to do 3 x 4 minutes at V02max, you can hit that power output exactly and hold it, thereby inducing a consistent demand on your muscles and maximising the potential training effect. In essence, it strips out any surging in your power and allows you to hit a specific wattage and stay there for as long as you need to hold it. 

This works often by magnets in the trainer controlling the velocity at which the super-efficient flywheel will spin at.  In fact, there will be a specific velocity the flywheel will want to spin at and if you get it to that point it will in effect find a ‘sweet spot’.  All you then have to do is keep pedalling hard enough to maintain that flywheel velocity.  If you pedal too hard, the flywheel will go ‘light’ and therefore, prevent you from putting out significant power above the velocity it wants to spin at.  So not only does it help you hit a specific wattage but it can also prevent you from riding too hard and spoiling the session objective.

It’s an awesome development in indoor cycle training, however, as a coach, I do fear many have become too reliant on it as a tool.  This is totally understandable because it does enable you to really control your training and quantify the effect it will have.  However, hitting a specific power at the exclusion of all other factors that contribute to improved performance shouldn’t be your only motive.  In this article we will run through the pros and cons of ERG mode and when/when not to use it.


There are many advantages to using ERG mode in your session, here are just a few:

It allows you to hit a very specific wattage

This means there is no guess work in whether you are putting in the requisite effort.  ERG mode will run at a percentage of FTP and you can build an entire training session around how it will respond and know you are doing exactly what is meant to be done.  This enables you to quantify and progress training sessions in a precise way.  So your 3 x 4 minutes at V02max can become 3 x 5 minutes and you can quantify accurately, the fitness improvement as one session will involve the exact same power output but has progressed to keep you there longer.


It simplifies your training immensely

So if you have a coach or a training plan, there is very little thinking to do. You just need to pedal to get the flywheel to the correct velocity and keep working to keep it there.


The training effect is not compromised by terrain or other variables such as rolling resistance etc.

ERG mode creates a more scientific and controlled training scenario.  So there is no drop in power as you freewheel down a section of descent or struggle to maintain a lower power going up an incline. You have all that uncertainty removed.


It can be used to encourage a higher cadence

Depending on what software you are using to set the trainer or plan the session, you can set the flywheel velocity not only to respond to power output but also to a specific cadence.  For example, this means you can set its ‘sweet spot’ to 100% of FTP with a cadence of 90rpm.  Therefore, the trainer will spin up most comfortably if the rider hits this specific power and usually within about 5rpm of this cadence.  If the rider spins up too quickly, the flywheel goes light and if they allow their leg speed to drop too low, the flywheel will become increasingly heavy.  Think of it as like a fixed gear or track bike in this respect.


It allows you to relax and simply focus on working hard

There are occasions when you just want to suffer and not have to think about anything else.  In this respect in can be good for your mental well-being to do a session in ERG mode because the trainer will adapt and all you need to do is pedal.  Assuming you’re not working super hard, it means your mind will be able to drift as you check out for a bit.


This is where things might get a bit controversial as not everyone will agree with what we would consider cons and some of them just plain contradict the above! Put simply, the cons are context driven but there are some key downsides to be aware of:

It can be horrendous if you’re not on a good day

Because ERG mode requires you to push a very specific power output and specific cadence range  (usually between 80-100rpm) in order to keep the flywheel turning at velocity, if you are a touch fatigued, haven’t eaten enough before the session or are simply on a bad day, it can mean the session turns from a challenge into a massacre.  This is because if you are unable to keep within the required power and cadence ranges, the flywheel will slow down and become heavier and heavier.  So think track bike again and how hard sprinters have to work to get that single big gear up to speed, that is the scenario you are constantly battling if your leg speed slows down.


You can forget how to produce power smoothly

One of the positives of ERG mode is it allows you to sit at a specific power and all you need to focus on his turning the pedals.  However, if you rely on ERG mode too much and use it for all your turbo sessions, it can see you almost forget what it is like to produce power without it! When we run sessions in the RIAK Fitness studio with ERG mode off, we can often tell who has a smart trainer and who does most of their riding outdoors.  This is because the owners of smart trainers tend to have far bigger peaks and troughs in their power output as they’re not used to riding on a turbo without the crutch of ERG mode.  This is a negative because turbo training is meant to be about developing a level of conditioning that you can directly apply to the road. But if your power is all over the place, you will not find a rhythm and will fatigue quicker out on the road than your actual fitness should dictate. It will also make you super annoying to ride with in a group as you constantly speed up and slow down!


The mind can drift too much and you lose focus

ERG mode allows you to minimise the things you have to focus on and you just drive those pedals round.  In some scenarios that’s great for your mental well-being but if your session or interval is a relatively light one and you have nothing to hold your attention, it can mean your focus drifts.  This often means you start checking your phone or other things to occupy your mind and can have a negative impact both on your mental well-being and the quality of your session.  Firstly, if you are checking your phone all the time it means you will still be connected to the world and all it takes is that message or email that for whatever reason gets inside your head and then that is what you’re really thinking about and not what’s coming up in your session.  Secondly, if your mind is elsewhere, it can really impact how you feel doing a session and make it so much harder than it needs to be.


It’s easy to just do a session in a plan and not really understand why you are doing it

ERG mode is great because you can create a session plan and it will adjust to replicate a percentage of your FTP, which means you can do some really cool dynamic sessions that you just wouldn’t be able to do out on the open roads.  However, if all you need do is pedal harder or softer in order to satisfy the session plan, arguably you are less likely to engage and appreciate what that session is meant to be about.  For instance, say your session is about simulating a race finish so you do repeated pickups off threshold.  If you’re doing this in ERG mode, you just pedal harder when you need to.  With it off, you have to focus on what you’re doing and be ready to drop that gear for the sprint or pick up.  There’s a real technique to feeding in a gear at the right time without smashing your chain.  Using ERG mode means you lose the opportunity to practice this.


It’s not reality

Linked to the above re losing the ability to produce power smoothly, ERG mode is one more step away from reality in so far as turbo training itself is already a step away because you have no atmospheric, aerodynamic, topographical or rolling resistance factors to deal with.  ERG mode is not realistic, it is about pure conditioning work.  Just worth remembering.


If your FTP is too high or too low, you will not be hitting the correct energy system

This is a key one because your FTP is actually a dynamic metric and different on any given day.  Your FTP is a rough measurement of your aerobic threshold and therefore, a measure of a metabolic process which is not identical every day.  There are a multitude of factors that will feed into at what power this threshold is actually met.  So having it set so specifically day in day out means that sometimes it will inevitably be too high and on others, far too low.  This is why typically, as athletes we work with power zones or training zones.  We work within a range because an exact number isn’t always attainable.  ERG mode, therefore, might see you on occasion missing your session objective because when you think you’re in Zone 3 (Tempo), you might actually be in Zone 4 (Threshold) and your heart rate is not where it needs to be for the training effect you desire.


It can prevent you from producing new peak powers and developing your anaerobic energy systems

This last point is a big one we try to repeat in our sessions regularly when they involve sprints or very high powered efforts.  FTP is one metric but your 5-minute, 2-minute, 1-minute, 20-second and 5-second powers are also super important metrics if you wish to be a well-balanced rider.  However, if you’re sprinting or doing V02max type work with ERG mode on, it is potentially going to limit your ability to improve on your short duration peak powers and you therefore, won’t have as good a gauge as to how your V02max and Anaerobic Capacity are developing.


When/When not to use ERG mode

It’s probably clear to you by this point that whether we would suggest to use ERG mode or not is entirely context driven.  It depends on what session you are doing.  If your session is purely about conditioning and has no sprints, ERG mode is probably a good shout.  A lot of sessions will fit this bill and for the most part, ERG mode will probably feature in most of your turbo sessions.  It’s therefore perhaps a bit easier so suggest when using ERG mode might not be advisable:

  • Where you have multiple sprint sets, so your peak power isn’t limited and you can see what your repeatability is like i.e. how close you can get to the same average power each time (your speed endurance).
  • When you are doing a benchmarking session. An example of a benchmarking sessions would be something like 3 x 10min at FTP because this is always a good indication of whether you are ready for an FTP test and you will want to see how your power and cadence fluctuates.
  • When you are not feeling great and the legs aren’t there, it is probably best to run the session out of ERG mode. This will allow your legs to find a point that you can hold and allow your power to surge and drop in-line with what your physiology that day can handle. You might actually surprise yourself by fulfilling the session requirements in terms of average power for the interval etc., you’ve just taken a different route to get there.
  • If you have had or are having a stressful day and you’re struggling to focus on your session, drop the trainer out of ERG mode as this will force your mind to focus on what you are doing to prevent your power from peaking and troughing too much.
  • If you are looking to develop your anaerobic system for racing, I would suggest that any work beyond V02max should be done out of ERG mode. This will enable you to track your short duration peak power and also make the session more realistic so you can actually replicate that power on the roads.


So there you have it. In short, just make sure you mix it up!