Long runs
The key to the program is the long run, which builds from 4 miles in Week 1 to 12 miles in the climactic Week 11. (After that, you taper a week to arrive at the half marathon well rested.) You can skip an occasional workout, or juggle the schedule depending on other commitments, but do not cheat on the long runs. Although the schedule suggests long runs on Saturdays, you can switch to Sundays or even other days of the week to suit your schedule.