Average power of laps in Strava is off


I’m not sure whether this is a Zwift or a Strava issue, but I figured I would start here. When doing workouts in Zwift it creates automatic laps for each interval. I noticed that the average power of the intervals is off by quite a bit.

For example, the average of the overs should be 365W and the average of the unders 155W. As you can see in the images in Strava it shows the average of the overs somewhere between 279W and 299W while the average of the unders is between 234W and 244W. It gauges the over too low and the unders too high.

Is this a bug? And if so, is the problem with Strava or with Zwift? I also noticed that the duration of the is usually one or two second off. But I don’t think this can explain the error.

Thanks in advance!


I asked Strava as well. This is what they replied. Does this make sense?

This is due to how Zwift writes lap data to the FIT file. When you begin your workout, the first few laps will actually be missing valid activity stream data, basically it will look like there is nothing happening in those initial laps. Upon upload to our system, the missing data is automatically discarded, and laps may look slightly different overall.

This is simply a limitation of the integration at this time. Apologies for any confusion or inconvenience there.

Looks like this bug still isn’t fixed, have anyone heard if they are working to fix it?