The last 5k race I ran was Zach’s Run on October 4, 2008. The last time I did anything resembling speedwork was about about 6 months ago, but even that was more like tempo running than all-out, out-of-breath, feel-like-my-lungs-are-going-to-explode running. Yup, it’s true: I can run 50 miles, I can do an Ironman, yet a 5k still scares me. It’s not the distance. It’s the speed. It’s the burning, searing pain that comes from pushing your body past the redline into anaerobic zone. True, it’s only little more than 20 minutes. But, those 20 minutes are grueling. It’s not like …