Ready to take on a 100-mile Ultramarathon? This training plan is 24 weeks in length. Weekly mileage tops out at 70 miles per week. Each training week will include details regarding cross-training and recommended pace zones. You should be able to comfortably run at least 35-40 miles per week for 3 to 4 weeks in a row. Our 100 Mile Ultramarathon Running Plan starts at 33 miles in the first week and builds weekly mileage from there. You will be doing long miles almost every weekend to prepare ...