Variable Time 2 or 3x 12min cont. (4m/1m/3m/1m/2m/1m) rest 4:00 ~50/~75% rate 20 2k PB pace + 22-24 seconds (or slower) on the longer sections (4/3/2m). On the 1:00 sections, aim for 2k + 8-10 seconds (or quicker).