A personal favorite that I liked to do abt once every 10 days, from start of speedwork up to abt 2 wks before race ...
"2 minute drills" (an homage to Roger Staubach, the only Dallas Cowboy I ever liked)
-- workout is done on an 11-12mi course, and gauge what's your regular middling-to-hard trainign pace which I call "steady-state rate", orr SSR, below --
- 10 min at SSR
- set of 5x (2:00 hard+2:00 at SSR) -- "hard" pace unknown, just run hard dammit
- 10 min at SSR
- repeat set -- 5x (2:00 hard, 2:00 at SSR)
- rest of run at SSR
If you're dong it right, the 4th & 5th trep of each set shd feel like torture, and transition to "hard" pace may be a barely discernible acceleration.
Worked for me.