Watch face for a workout

When performing a workout during running, Garmin adds an extra watch face automatically. It's the one were it has an arrow that tells you if you are inside your target pace, counts down on intervals etc.

I haven't found anywhere to edit this watch face. Many of my workouts are based around pace. I would be nice to add heart rate to that watch face so I can see if my HR corresponds with the suggested pace.

Thanks,
Espen