While determining my AeT using the DIY treadmill test, I notice a regular repeating pattern of my heat rate decreasing for a short time. Actually, I think it is always present during exercise, but it is only apparent when doing something like a steady, long treadmill run, versus a trail run on rolling hills. The first picture shows the regular decreases in heart rate, the second picture shows a zoom in to show that this is not a super short blip of missing data. Does anyone else see this sort of thing in their data? Any ideas if this is really my heart rate versus some fluke of using non-medical grade, ie sports equipment? For info, I have varied all recording equipment except for the HRM which is a Polar H10, and still get similar results. HRM strap was changed too with no difference.