Long runs are key parts of our training. If one is to be a middle or long distance runner, the Sunday long run is part of the program. Want to succeed, want to prepare your body to handle the speed days, then do your long runs.
Sunday: Long, relaxed run of 50 minutes. Suggest running with a group and get off the roads and run some trails. Keep the pace at conversational pace, the idea is to stay on your feet for the required time. Make sure that you cooldown and stretch, getting some water and changing out of wet clothes.