VO2-1 : VO2 Intervals -- 2x3x4(3)(10) -- 2 sets of 3 VO2 Intervals (Zone 5), each interval 4 min in duration. 3 min. rest between intervals, 10 min. rest between sets.

When you're not crushing it doing the VO2 efforts, you should be warming up or recovering in Zone 1.