Warm-up for 3 minutes
Sprint as hard as you can for 30 seconds followed by a slow recovery run for 90 seconds.
repeat 7 times
Then Sprint as hard as you can for 30 seconds followed by a Cool down for 2 minutes 30 seconds.
That gives you a good 20 minute work out.
This is the specific workout that I have been doing on the treadmill:
Warm-up for 3 minutes at a pace of 6.2 mph on a grade of 1.
The Sprints are done for 30 seconds with the treadmill set a grade of 5 and the recovery is done for 90 seconds at a grade of 1.
2 - Sprint 8.5 mph - Recovery 6.0 mph
2 - Sprint 8.7 mph - Recovery 6.0 mph
3 - Sprint 9.0 mph - Recovery 6.0 mph
1 - Sprint 9.0 mph
Cool down 2 minutes 30 seconds at a pace of 6.2 mph and a grade of 1.
I then take a short 2 or 3 minute break get a drink of water, wash the sweat off of my face and repeat the whole thing over again. That equals a 40 minute workout and running 4.4 miles