"Min/km" would be "pace", not "speed". To see pace instead of speed:
- in the individual activity, click on "Pace" under "Timing"
- in the "Full Page" (i.e., the spreadsheet-like report), you can select what data field you want to show (including "Avg Pace") in each column.
The problem is there is no "Avg Pace" in "Available Fields" in my "Reports" section. Maybe I'm looking for this in the wrong place. I tried this path: Analyze-> Reports-> Progress Summary-> Customize.