Patrick,being fairly new to running I didn't really appreciate the changing of trainers, about 8 months in I had sore shins and a sore knee, I came on here and asked advice and like the guys say it works,invested in good trainers that matched my workload and haven't looked back, hard to do ,but, might be worth missing the 10 miler, if u r well ,if u can do 8 u can do 10 , also mark said earlier ,there are so many different race meets throughout the year is it worth crippling yourself for ??