It would be great to be able to zoom in further on selected sections of the HR graph. I would find it very useful to analyze just a section, perhaps take a closer look at an interval.
I had the same problem. When I tried to zoom in on the graph in Garmin Training Center the HR and speed and elevation would all separate out of view from each other. I could not tell what was going on between them.
I solved it by using "auto laps" set by distance of 0.5 miles. That generates a lot of laps and you do not have to look at them if you don't want to but if there is an area where you want to see your data in detail just click on the laps. Works great for me.
