If your at this level and are reading this, you've humored me enough to keep going and could potentially write an article on this web site about how you go about your training. Since Deena Kastor and Meb Keflezighi are not here to add some advice, I will risk myself and add my two cents to this level of running fitness.
First thing, and expert runner should be able to run in the zone 1 range all day long, barely breaking a sweat. These athletes are fine tuned running machines and have close to the same body fat as an average model on a cat walk. That said, the muscle mass is fine tuned and the heart is usually as big as a football :0).
I have one friend who's an ultrafit retired cyclist (retired from all out competition but still competes at the fun level) - I put him on my treadmill with a heart monitor and asked him to start running. When he reached my top speed that I could sustain for more than 5 minutes (11 km/h) - his heart rate was barely beating. He could run at this pace for hours, I could barely do it for 5 minutes.
That's the difference between jog runner and Meb Keflezighi, the ability to achieve a speed and endurance that boggles the mind, strains the body, and pounds the heart.
These people usually have trained since they were kids and benefit from coaches and proper climate atmospheres (high altitude training) to enable them to reach the next level. They also have a very strict meal regiment and cannot afford to indulge in life's simple pleasures (Beer - wine - cheese cake ...) without paying a hefty price performance wise.
