Here are four excellent videos featuring 2008 USA Olympic 5000m team member, Matt Tegenkamp, showing his core routine. It features core work that involves balance and joint mobility along with strength and flexibility. I like some of the variations of familiar exercises that I have tried previously. I also like the adductor work during Part 2. I think this will be very helpful for me.
Part 1: The Warm-Up
Part 2: Floor Routine
Part 3: Dumbell Routine
Part 4: Balance and Glute Routine
Here Matt and Jonathon Riley demonstrate some range of motion exercises that they complete after a run. It is interesting to see what the elites do!