AM / PM Practice
10 min. warm-up
3 x 6 minutes
5 minutes rest in between

Start out at 5k pace +2. After 1 minute, increase the pace to 2k pace +2 for 1 minute, then go back down to the original pace. Continue to alternate between these two paces every minute for the duration of the 6 minutes. The rate should move between 26 and 28 or so.