… there are lots of workouts runners can–and should–do regularly. Training variety improves your fitness, staves off injuries, and keeps motivation high (plus it allows me to eat more of my wife’s lasagna). But if pressed to name the one workout that has the greatest impact on racing performance at any distance, I’d answer with a clear conscience: the tempo run.
Tempo runs will make you a stronger miler, a faster 5-K runner, a more powerful 10-K runner, and a less-fatigued marathoner. How can one workout benefit such a wide range of race distances? Simply put: Tempo runs teach your body to run faster before fatiguing.
Source: We All Need Speed
I’m still weeks away from even being able to run 
My Warfarin Diet 