Hills (for me, bridges over the Intracoastal and I-95) start this week on our schedule. Here's suggestions from Jeff Galloway, for sub-4 guys. Run these hill workouts, once a week, over the next 4 or 5 weeks; maybe we try to run 4 of these during this six-week session:
4-6 hills in a 5-7 mile run
7-8 hills in 7-8 mile run
9-10 hills in 8-9 mile run
Pick a hill 400 to 800 meters long, gentle grade and run at 10K speed or a little slower (8:50 to 9:00's is probably reasonable), don't sprint. Run up and over, and walk down.
He insists hills build leg strength that weights can't duplicate (static vs dynamic), and that hills should be done early in the schedule (he's scheduled hills 23 to 28 weeks before race, which is where we are now, taking out the rest weeks) and before speed work starts.