Indoor Training

The Myth of Smooth Power Lines

When using ERG mode, some applications or smart trainers smooth out the power for you, so you think you are constantly pedaling at your target watts. That would be nice, wouldn’t be? Unfortunately, that’s not how power meters really work. Most powermeters measure power throughout the pedal stroke and many high-end smart trainers do something similar. Your power will vary as you are pushing down and pulling up the pedal with each revolution.

If you watch your power in real time – without any smoothing – you will see numbers all over the place. Bike devices like the Garmin Edge or Wahoo Element, have power averages as part of their field selection. You can select 3s or 10s averages. If you are looking at real-time power numbers, you will probably go crazy so selecting one of these averages might be a better choice. I personally prefer the 3s average and that’s what I usually have displayed on my bike computer.

Some training application, such as TrainerRoad, offer power smoothing that you can turn on in the settings. Some bike trainers estimate power and usually show you smoother numbers.

Here is an example of a workout I did using my Wahoo KICKR and TrainerRoad in ERG Mode and power smoothing turned on. You can see how smooth the power line look. It looks pretty, doesn’t it?

 

However, let’s take a look at the same exact workout but without any smoothing. This graph doesn’t look pretty at all. You can see how my power is all over the place.

So next time when you are ready to workout on your smart trainer, it’s normal to see power jump up and down. Some bike trainers react to changes in your pedal stroke faster than others – but we are talking about split seconds. Also, switching to a smaller ring when you are in ERG mode can help smooth out your pedal stroke and you will see a smoother line.

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2 Comments

  • Thank you for the article. Its reassuring to know my “rough” power lines are normal. How many seconds is recommended for power smoothing? This is for the manual setting, especially when taking FTP tests.