Training: What is ERG mode and should you use it?

If you have a modern “smart” turbo trainer then chances are it’s capable of being used in ERG mode. But what exactly is ERG mode? Should you use it? And will it make you a stronger, Strava segment smashing, cycling beast?

ERG is short for Ergometer. It is when your turbo trainer automatically selects the resistance – and hence wattage output – for you. Say your interval calls for 250 watts; it doesn’t matter if you are in your 36/26 or 52/12 gear, your trainer will automatically control the resistance level to keep you outputting that 250 watts. You can set these levels using your Garmin or Wahoo head unit, but it is best used in conjunction with a programmed workout (loaded into Trainer Road, Zwift, The Sufferfest, etc).

View from the trainer; locked and loaded!

Your turbo trainer takes full control, so all you need to do is pedal hard and feel awesome. My preference is to whack it in the big ring and a rear cog which gives a straight chain line, then get cracking! (Note: If noise is an issue when/where you train, switch to using the inner ring and a larger rear cog).

There is no hiding in ERG mode. You’re going to be crushing that 250 watts so just buck up and deal! There is no 220 watts, no 260 watts, you’re holding a (relatively) steady 250 for the duration of that interval. If your power starts to drop off or your cadence falls slightly, the trainer will adjust the resistance to push you back up to 250 watts! Conversely, go too hard and it’ll ease you back down again.

Green line is my actual power, using ERG mode it tracks almost exactly over the grey area (prescribed workout power).

ERG keeps you honest. Not only will you hit the correct high power numbers, but you will also recover properly in between. Many cyclists will ride too easy when it’s meant to be hard, and also too hard when it’s meant to be easy! A well designed workout will give you just enough rest at just the right wattage for you to recover just enough to hammer the next hard interval. Go too hard when you’re meant to be resting and it’ll be detrimental to the following efforts. ERG mode will keep you spinning at recovery watts even if you’re tempted to push harder.

Training in ERG mode takes some getting used to and some trainers are smoother than others at making these adjustments. Budget model smart trainers can take 5-10 seconds to change resistance between intervals, and the same amount of time to make each little micro adjustment. That’s no good if your interval is only 10 seconds long! This is not an issue with higher end trainers, which handle these resistance adjustments almost instantly.

Where ERG mode does fall down slightly is if there are big variances between the rest and work wattage. Say you are recovering at 120 watts and need to go into a 750 watt sprint interval – the trainer is going to clamp down HARD and you need to be ready to jump on the pedals. Mis-time that change and you’ll either spin out before the resistance changes or not be able to turn the pedals as the trainer cranks up before you do!

When NOT to use ERG mode. If you are doing any power testing, where the goal is to hit your max numbers (whether that be for one minute or twenty) then turn ERG mode off. You don’t want the trainer dictating wattage during a test, you want total control over your badass power output. Leave your trainer in basic or slope mode and control power the old school way using your gears.

Also, if you have a budget smart trainer that struggles to make fast and accurate adjustments, ERG mode is best left for workouts with longer intervals. It may be best to disable it for sprint workouts.

About to climb aboard and CRUSH my next workout session!

More precision, less fuss. Personally, I use ERG mode on my Tacx NEO for all my workouts. Having my power levels locked in is one less thing to concentrate on when I’m at my limit, sweating buckets, tongue dangling above the stem. ERG mode ensures I maintain the correct wattage when I need to and then recover properly between those big efforts. I simply choose my gear ratio, lock in the correct cadence and concentrate on crushing my power targets. Job done!

8 Comments Add yours

  1. ive been trying to figure out the erg mode whether i need it on or not. a few updates back caused me to shut off my Zwift account as before the updates everything worked perfect and i was riding 120 miles per ride, then the updates came out causing a reconnect of trainer etc and since then all the way up until now it’s been difficult to even pedal on zwift and im a climber in real world. i appreciate the article.

    Liked by 1 person

    1. I’ve heard a few others have had a similar issue since the update. I haven’t tested it as I’ve been off Zwift since my Broadband cable got cut! Using ERG mode is best for workouts, not really for riding Zwift in free ride mode.

      Liked by 1 person

  2. typevertigo says:

    Fast fact: An “erg” is also a unit of work and/or power. Yes, just like a watt and a horsepower (~750 W) are.

    Good read.

    Liked by 1 person

    1. Interesting, thanks! :-)


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