A similar workout, but one that is much, much harder, is 12 x 400m with just 30 to 45 seconds of jog/walk recoveries. Simply put, you run race pace for one lap and when you finish that lap, you jog around (or walk if you have to) until 30 to 45 seconds is up. Then run another 400m lap at race pace. Ideally you should run repetitions 10, 11 and 12 fast, faster, fastest, practicing what you hope to do in the race, which is speeding up at the end. I wouldn't advise this workout in the first couple of weeks of training, but definitely do this workout at least once after your baseline race and before your goal race.
Another piece of the puzzle for good 5K training plans is strides, or short intervals that are completed at an effort faster than 5K pace. These should be done twice a week as part of your easy day runs. Stride for 20 to 30 seconds at just faster than 5K pace, followed by a 60-second easy jog. Do 4 to 5 strides in the last half of your easy run.
If your easy run is 3 miles, then you might run the first 1.5 miles easy, then begin to run your strides as part of your easy run. Strides are important because they remind your body that it can run faster than 5K pace. You don't want to become the kind of runner who can't kick (pick up the pace) at the end of the race, nor do you want to become the kind of runner who can't run faster than 5K pace.
You should also complete strides as part of your warm-up on workout Tuesdays, and before your long run on Saturdays, as they will make the paces you run during those workouts feel easier because of muscle memory—your 5K race pace and your long runs will feel easier because you very recently ran faster than your 5K pace.
More: Run Fast With Strides
5K Training Plan Step 6: Strength Training
The final piece of the puzzle for 5k preparation—and all run training—is to complete enough ancillary work (strength training) to support the work you're doing. Complete the Lunge Matrix before your runs, then do some general strength and mobility exercises or active isolated flexibility after your runs. This is crucial for staying healthy.
General strength routines done throughout the week will change your endocrine profile, and the older you get, the more important this becomes. So add some challenging general strength routines at the end of your Tuesday workouts and Saturday long runs.
Have fun with your 5K training, knowing that you'll make a mistake or two in training, but if you learn from those mistakes, you'll train even smarter in the future.5K.