Ah. Forgot to tell you. I've done 400's as well. 10x, 12x and 15x400. Average around 1'19-1'21. This was maybe 5-8wks ago.
Did an easy jog as first session today after the marathon I ran on Saturday.
I never train with heart rate monitor, so I don't really know my zones. However, I did a lactate test once, on a treadmill with the following results:
Max pulse: 187
Anaerobic threshold: 170 (3'52min/km)
Aerobic threshold: 155
Lower limit for aerobic zone: 142
Max O2 consumption: 63,2 ml/kg/min (4,62 L/min)
Max energy consumption: 23,1 kcal/min (96,7 kJ/min)
I know it was a six years ago, but it might give you some help.
I also do know my resting rate (usually taken at 09:00 in front of the computer) is around 38. In peak shape it drops to 34.
So. 4k test tomorrow? 4days post marathon, but that's fine.