Warm up 3x 1200m @ 10k pace; 1 min. recovery2 x 800m @ 5k pace; 2 min. recovery2 x 400m @ faster than 5k pace; 200m recovery (now, if you want to add to this workout, then add 1 more 800, and 1 more 400m). That's a decent workout of changing paces, working your way...

 Warm up.  800m @ 5k pace 400m recovery jog (run this reverse direction- outer lanes or on the grass) 300m @ mile pace (if you don't know your mile pace, then run fast) 200m float - Float is close to your 10k pace. Go right back to the top - 800, 400, 300,200.  Your...

Warm up. 1k/800m  Run 1k @ 10k pace, go right in to an 800m @ 5k pace; 2 min. recovery.  3 sets.  (5400m, not including recovery jog). Cool down

Warm up 10x 500m (my favorite workout) @ 5k pace or a pace that you are comfortable at; 100m or across the field recovery. (short recovery....again!!!) Maybe do some 4-6 x diagonals. Finish with a 1-2 mile cool down.

Warm up. Turnaround 200's.24 x 200m @ 5k pace; 40m recovery. This workout goes quickly, recovery is short, like the intervals.4-6 x diagonals. Cool down.

Warm up. 1 x 1600m @ Threshold pace - about 20 seconds slower than your 5k pace/mile.1 min. recovery.8 x 400m @ 5k pace; cut across the grass to the start for your recovery. (so - short recovery). Dessert: 1 x 800m @ faster than 5k pace. Cool down.

Workout is 400's 4 x 400 @ Threshold pace (10k pace); 100m jog recovery4 x 400 @ 5k pace; 200m jog recovery4  x 400 @ 1-3 seconds faster than 5k pace; 300m jog recovery

Good warm up and Cool down. 800m @ your 10k pace. Recover - 200m. Then:  16 x 200's @ 5k or faster pace; Recovery jog is across the field - diagonally back to the start. Dessert? finish with an 800m @ 10k pace. 

Warm up 4 - 5 x  800m @ you choose the effort.  10k? 5k? Mix it up. Run #2 and #4 hammering the last 400m of the 800m interval. (Or run them all at 10k pace; hammering the last 400 2 out of 4 intervals).  Example: do  1 x 800m @ 10k; 1 @ 5k; 1 @ 10k; 1 @ 5k   2 min....