How long was the rest between 400s and how hard it felt ~ 8-9 bouts?
1:30 rest, it was supposed to be 1:10 but it was very hot and humid so we added more time. I felt pretty good the whole time and stayed on pace for the most part- some a couple seconds slow, some too fast. I probably could have done a few more intervals on pace.
10 is max for this type of workout that is 4 km of hard running :), rest time has to be adequate, do not push it :)