Is multiweek intervals of the same mileage with jumps set at even intervals throughout the training period more effective than a linear progression? I've heard that the subsequent fitness gain from making mileage jumps is higher that way (from Daniels' I think) but I don't know. What are your thoughts? Also, if using the interval plan how many weeks in between jumps? And how big are they? My understanding right now is adding 5 miles after every three weeks, but it might depend on what the mileage is compared to your previous experience. How should it be if you are running more than you ever have? Discus. Take into account injury prevention and fitness gains.