Workout:

4 -5 x 1000 @ 10k pace; 1:30 recovery jog.

4 x 400m @ 5k pace; 200m jog recovery.

If you’re training for a 5k, then run

 3 -4 x 1000 @ 5k goal pace, 2 min. recovery.

2-4 x 400m faster than 5k pace (a few secs.); 200m recovery jog.