I ask this question because I had done a lot of treadmill running before I started using the suggested workout feature recently, and I think the data might be confusing it. The suggested paces were very slow and when I switched to HR target the pace was about 30 seconds faster.
Reasons why the treadmill data could throw the algorithm out are that I find I run faster at given effort level on the road, but also that much of my treadmill running is on a slope and Garmin only sees the pace, not the slope.
Anyone know the answer?