Use a treadmill, set at 12% grade at 0-30 sec slower pace per mile than best 5k pace. Do not reduce the speed!
Remember, a tabata is 20 seconds work, 10 seconds rest, for 8 intervals. 4 minutes total.
This workout is from CrossFit Endurance.
If you do not have a treadmill, run from home. I suggest you run the first 4 intervals away from home, as fast and as far as possible. STOP in place when you have your 10 seconds rest. Run back home for the last 4 intervals. This will give you a good indication if you were able to hold your speed for the entire 4 minutes.
We did this last on Oct. 11