Polar watches export FIT files through Polar Flow. Import into MetricsOverlay to add overlays to your video.
Export: Polar Flow web → activity → export → FIT.
Polar records heart rate (known for accurate optical HR), pace, speed, cadence (with running sensor), altitude, and GPS.
Polar doesn't record running power natively. If you pair a Stryd or other power meter, that data will be in the FIT file.
Heart rate from Polar tends to be clean and consistent, so the HR overlay looks good without adjusting interpolation.