Using the FR955 metronome with vibration (180 bpm, every 4:th Beat, no Tone) screwed up much of the data points of the Run today - easy, smooth run on asphalt:
https://connect.garmin.com/modern/activity/12538948774
Eg Stride Length has many points of gigantic strides - 1.93 meters asf. Cadence has points with zero (0) spm or half of the metronome - in the 90-ish spm. Power at times goes down to zero Watts (0) and overall has a very jagged profile. Vertical Ratio and Ground Contact Time similarly exhibit disturbances which are more pronounced in the compressed graph of the phone connect app than at the Web connect view.
Usually when practicing cadence I use specific cadence music or set the watch metronome to use sound only (Tone; holding the watch close to an ear now and then to actually hear it). This run was the first use of vibration. The watch is snug on my wrist. No HR sensor problem. A Coros Pace 2 on the other wrist gave an average of 179 spm (FR955 170 spm because of the disturbance) with 0.92 meters Stride Length (FR955 1.00 meters).
Searching these Garmin forums for metronome posts I found a few similar observations when it came to the FR245 watch quite a few years ago:
I don't expect Garmin to change the algorithms to compensate for metronome vibrations, but wanted to post about the effect here for other runners to be aware of.