In the past months I have been running in an indoor track and every time the watch (Garmin-Fenix 6) shows paces like 5:20min/km but I feel I'm running below 4:15min/km (my usual pace in Z1-2).

A friend of mine has joined me in some runs and he use a Garmin Foot Pod garmin watch, turns out that I have been running at 4:20min/km all this time, based on his stats as we have been running shoulder to shoulder.

Last night, when running with my friend, I started shaking my arm with the watch on it, we were running at 4:40min/km, based on his Garmin Foot Pod garmin watch, but my watch was showing <3:15 mi/km just by shaking my arms as if I were sprinting.

When I run, I don't shake my arms (up/down) lots so I think I need to move them more as if I were sprinting to have accurate readings? but my technic is not like that and I dont want to change it just for the indoor track.

My friend has suggested to me to get a Garmin Foot Pod but they don't sell them anymore. I was about to attach the watch to my foot to have more accurate readings.

Any suggestions?

Thanks