Welcome to today's NYC Marathon chat with two-time winner John Kagwe. Thanks for spending some time with us. Speed work should be done all the time. Two times a week is a good practice.
Speed is the determining factor for the marathon.
You move with the speed and the endurance for the long run. When you are running, you do so with speed and endurance. I do long run workouts. Like 10 miles to 20 miles for two weeks then you start speed training. Then you go on to two weeks of speed training, every week I do speed on Wednesday and Fridays.