I felt like I phoned in the running pace a bit. I thought I was getting lady cramps, so I lost focus and found excuses to back off. But I still got 21 splat points (13 minutes in zone 4, plus 8 minutes in zone 5), so maybe that's not the point? I'm not sure.
When training heart rate... would it be better to be at the bottom or top of the target zone? Like, better to just barely be in the zone, so it's faster to recover from the workout? Or push the top end of the zone, to increase the size of the zone? Or perhaps it just depends on what your goal is.
And anyway, if my goal is weight loss first (performance second), then time spent in zone 4 is more valuable than zone 5; and in that case, backing off makes sense. Hmm.