Warm up: 1-2 mile light jog. Then for 30 seconds I gradually speed up to about 90% of a sprint for 30 seconds and slow down to a walk for 30 seconds, then walk/rest for 30 seconds. I repeat this same 3 more times. The 3rd time I do it the first 30 seconds I do butt kicks and the 4th repeat the first 30 seconds I do knee highs. **The warm up is super important to this workout. I skipped doing the full warm up one time and will never do that again because it made the rest of the workout so much harder.
Track Repeats: The easiest place to do this is on a standard 400 meter track. Total I do around 3 miles of track repeats. Usually I do 6 x 800 meters. This is speed work so I run each 800 meter about a minute faster than I would run a normal 800 meter (half mile). Then I walk/jog for half the amount of time it took for me to run the half mile. Sometimes I switch it up and do 4 x 800 meter + 4 x 400 meter switching off to keep things interesting. I just try to make sure to do around 3 miles of speed work. Total it ends up being between 5-7 miles of running/jogging/walking.
Cool Down: When I'm done with the track repeats I just make sure walk for at least 5 minutes and stretch a lot.
This workout is strenuous and exhausting. If I'm just getting back into running I have to work up to running the full 3 miles of speed work and sometimes it takes a while to get to that point. It's really easy to get injured doing speed work so you have to be patient with yourself.