I'm trying to understand the Average Power Phase values inside the .fit file. There are four of them, for example avg_left_power_phase: (355.7812555590821, 199.68750312011724, 202.50000316406255, 97.0312515161133) for certain lap. I assume that the first is the start of the peak phase, the last is the end. But what about those two remaining? Similar four values are for peak power phase, for example avg_left_power_phase_peak: (59.06250092285158, 125.15625195556643, 66.09375103271486, 91.40625142822267).

I looked to the fit file specs, but there is nothing.

UPDATE - I'm using Favero Asioma Duo power meter pedals. They have implemented all Garmin PCD metrics, except the cleat offset.

  • I have a hunch that these parameters are related to something like pedaling smoothness. I'm honestly not familiar enough with this parameter or with FIT file outputs to really provide good guidance here. Can you edit the question to say what power meter you're using? I have a hunch from the tags that it's the Garmin Vector, but you should say explicitly.
    – Weiwen Ng
    Jun 10, 2020 at 12:12

1 Answer 1


Looking at the ANT+ Power profile from this page. 'Power phase' and 'power phase peak' are different.
'Power phase' is where the positive contribution starts and ends. 'Power phase peak' are the start and end of peak power is being produced. Peak power is potentially a configurable amount but defaults to 50% of the total power. Angles are measured clockwise from vertical.

The 4 number you have are Start angle, End angle, Arc length and Center. This is from looking at the FIT SDK. The arc length and center look sensible given your numbers.

  • Thank you very much. You answer help me a lot. I figured out those first three by comparing the file data with Garmin Connect, but I was wondering about the fourth one.
    – JirkaV
    Jun 10, 2020 at 15:37

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