008 - What is ERG mode and does gearing matter?

As more of us gravitate towards smart trainers, it’s worth learning about how they actually work so we can use them properly. Basically the trainer handles the resistance changes for you when riding, but it does have some behavior worth noting. This 12 minute video is the best explanation I have found:
How does this affect me?
First, as per the video, you need to test your FTP using your new equipment and set the value to get good performance from the machine. FTP values from your old equipment may not be accurate on your new machine so retest. Every software program requires this so make sure you FTP test and set the value in software.
Once this is set up, the trainer should give you good target power and resistance in your workouts. You should be able to get on and ride and it should feel like riding outside. But probably harder.
What gear should you use?
Technically, if you are doing target power training in ERG mode, gear selection does not affect your training. 260w is 260w in any gear. Some instructions tell you to chose a gear with good chain line, but there is more to know. Ideally you want to strive for good cadence which is typically 85-95, but may be higher for sprints and lower when doing slow speed work. The instructions inside TR and Zwift workouts will often indicate what cadence to strive for. I have found that certain gearing (52t x 12) allow me to hold my target cadence at 90+ so I usually use that gearing. If my cadence starts to drop, shifting up one gear (easier) often helps me keep my cadence up. An easier gear combo has slightly different leverage action from harder gears, and when you ride in a harder gear your flywheel has greater momentum which also factors in. So, you should experiment a bit with gearing to find a combination that allows you to keep a good cadence for yourself overall with expected ups and downs sometimes.
And, there is also some validity to using appropriate gearing on the ERG trainer to better target different muscles that are triggered by different gearing. So think about what gears you use outdoors and try those to start. For mountain bikers, I suggest starting with your big ring and 3 or 4 down from the top easiest gear on your cassette.
he short answer is:
“Ride in gears that simulate what you’re riding is like outside.”
For more technical detail, watch this video,
Does Gearing matter in ERG mode?
How do I do things?
So by trial and error, I seem to have figured out most of how to work in ERG mode to keep good intervals and avoid the Spiral of Death. That said, I’m still learning how to maximize my time on the trainer.
Although I mostly use Trainer Road and do structured training, I also use Zwift in freeride mode so I can ride around , race and practice changing gears specifically when climbing. It’s an excellent way to understand your gearing combos and your wattage output so when you get outside you can ‘replay’ what is working from your training. I don’t have power meters on my bikes so I use feel and instinct outside.
I have also started shifting to harder gears when doing low cadence, high power intervals so I don’t have to slow my cadence early in ERG mode to get higher resistance. It feels right to me and my Kickr reacts very quickly so it seems to be good. It’s working for me.
If you have any tips of your own, please share in the comments.
Happy training.
You beast.

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