Why distance runners should SPRINT!

Most distance runners don't like to do speed work, especially sprints, but that's because most don't know how good it is for their development! Here are some quotes that I hope will convince you:

              "The other main component of a kick is having the ability to recruit additional muscle fibers when fatigued and call upon our anaerobic energy reserves.  Before working on the ability to use these under fatigue, we have to increase the total capacity of each of these which are done through similar mechanisms.

                We have to lay the foundation and develop the ability to recruit a larger percentage of our muscle fibers  in a fresh state first.  No one can fully recruit all of their fibers because we have some protective mechanisms involved to prevent this from happening as catastrophe would likely result.  However, you can train to edge the percentage of fibers you can recruit towards that 100% max.  Research shows that elite athletes in various sprint or explosive events are much closer to max recruitment than regular athletes or untrained people. 
                To increase total fiber recruitment, we need to do activities that have a high force requirement and ideally do so in a specific running manner so that we recruit the same muscles in the same sequence that we do when running.  For distance runners, this simply means we need to sprint!"

- Steve Magness, coach of an 8:55 3200m high school runner and current assistant coach to Alberto Salazar (the one that coaches Galen Rupp) at the Nike Oregon Project 

             "If I go five kilometers, I use 20% of these fibers, always the same 20%. If I go a little bit faster, maybe 50, maybe 60, but when I never go for max intensity, I have a big percentage of fibers, maybe 40 percent, that are not activated. So when I need to use these fibers — because I am in the final sprint or because I finish the storage in the other fibers — I need for the last five kilometers, the last two kilometers, I need to take something. These faster fibers are not good for marathoning, but inside there is something I can use. The only way for using these is by doing short sprints. 
               To explain to a marathon runner that if he goes two times a week for a shorter sprint is good for improving endurance or resistance is difficult, but it's true."

-Renato Canova, World Renown Coach of World Champions & World Record Holders

Joe Vigil (former coach of Adams State) also says he uses sprints year-round to develop the anaerobic alactate system - "90-100% intensity sprints".