Should I continue wearing flats?

what was your buildup/history before the 12 weeks of 80-120 miles? were you running mostly on roads or on trails? what kind of pace were you running? there are a lot of variables to consider.

Yeah I guess I didn't think about that. Well let's see, I was a frosh in college when doing that mileage. Before that, before my junior year of high school I ran on and off at 60 and 100 miles a week, then during track season ran between 50-60 miles a week and ran 4:30 and 9:54 and 16:01 (1600,3200,5k). Before senior year in HS I ran between 90-115 miles a week in the nike pegasus and structure triax. Got a stress fracture in my medial tibia right before beginning of season. Senior year of track I ran between 40-80 miles a week and ran 15:54 for 5k on the track and was wearing the nike zoom elites at the time. Summer before frosh year in college i was using 2 pairs of the ultimate 81's going between 80-120 miles a week. Now that I look back I know that was way too much mileage to keep consistent with, and would have been perfectly fine between 60-80 at max. All my runs are done on trails, a few on roads to get some strength in the bones and such, ice baths daily for below the knees, morning runs mon-fri and sunday, but all morning runs around 8:20 or slower pace, afternoon easy runs starting out around 8:20 and lowering to 7 flat near the end. Basically JK methods.

If those 81's are men's size 8.5 or 9 I'll take 'em off your hands if you want.

so it's between flats and NB 900's?

i don't see all that much difference. why not rotate a little. 900's on roads or something. my 900's injured me so i'll never wear them again