Why are there spikes in my GPR?

Have you noticed what appear to be power spikes in your pedaling review charts? Unfortunately this is caused by an error in the way Garmin devices calculate pedaling effectiveness. Since your gross power absorbed (GPA) is calculated using L/R pedal balance and other variables, the faulty calculation can affect the workout summary and review.

To explain, let's use an example of a hypothetical workout with the following data:

  • GPR-right = 6321W (astronomical)
  • Power = 129W (reasonable)
  • Power Balance = 51/49, or .49 (reasonable)
  • Right Pedaling Effectiveness = 1% (really, really low)

Right pedaling effectiveness is a channel from your device, not from WKO4. For this workout, the device indicates that the right leg was only 1% effective, meaning the net power reported is 1% of actual power produced.

The problem here is that the right side pedaling effectiveness has a spike downward, saying that the right leg was only 1% effective for a second, but the power for that leg was 63W. So if the effectiveness is 1%, that means that to produce 63.21W at the pedal, the leg was producing 6321W total watts, 63.21W of which is the net force after overcoming 6258W of counter-power from the left leg.

Algorithms and models always depend on the data they run on. In this case, what looks like a spike is actually an error in the data collected by the device. We will look for future developments from Garmin to correct these errors. 

To repair your data in the meantime, you can delete the offending values from the right or left pedaling effectiveness data channel using the Sensor Data chart. Locate the row with the pad value, double-click the bad value, backspace to clear it, and click enter.


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