Hi,
In my past trainings I had always some low aerobic trainings and some high aerobic trainings. I was using the Edge 840 with hear rate sensor. Since some weeks I'm using my new Garmin forerunner 970 to broadcast the heart rate and I Garmin Conncect tells me I have an high aerobic shortage. It actually is zero even when I was in zone 3 and 4 for some time. Heart rate zones seems fine on Edge and Forerunner. See a lot of topics on this issue on the forum but no solution. Any help is appreciated. Thanks