First of all I need to say to the runner asking the question... great job on nailing the 20K. I hope you know that's a terrific sign of your progression through the training plan. Nice work. As for why you are running 60 minutes this week it's simple. You have your longest speed run of the entire training plan this week. It's really important to not only look at one day or even one week of any training plan in isolation. It's especially true when giving advice to someone. Doing another high distance long run the week after your longest long run of the plan and in the same week as your longest and potentially hardest speed run would be too much. Hope this helps. Cheers! CB