What is the purpose of adding doubles into your schedule? Generally speaking for aerobic development a single run of 10 miles is better than 5+5 or 6+4 or whatever. For most people the purpose of doing doubles is adding mileage. One could also be adding a shorter easy run to a hard workout day so that one run can be of a higher quality (faster). Another reason to add a second run is if you only have time to fit in x miles at one time but want to do more later, in other words you only have time to do 6-7 miles before work but want to get in 10 miles for the day you could do another 3-4 miles after work. I would also ask why you are scheduling the doubles in the way you have, you have a total of 10 miles on Monday, but in a 2x5 mile set, most folks doing doubles will have a shorter run and a longer run not two of the same distance especially given that you are normally only running 3-6 miles in a day that isn't your long run. Also, in your singles schedule you take Sunday off, but run 3 miles on the double schedule, why? Given what I've said I think staying with singles would be best for you, but I would lay out the week something like this: sun 4 mon 4 tues 8 wed 4 thurs 0 fri 4 sat 12 It still adds up to 36 miles and you get a day off, the slightly longer run on Tues reinforces the positive effects of the long run.