I have no proof for the negative/positive effect a heel-toe drop will have on anything but the smaller the difference when changing shoes the better it should be. The therapist who treats my ITB issues said stick to the shoe you always use as manufacturers are aware that people tend to stick to what works for them more often than not. I am relatively new to the running scene as it has only been a year since I started running seriously. I only use Nike in general, and the Free Run model specifically for running. I am onto my 3rd pair, still using the 2nd pair from time to time, and I have 2 more pairs waiting in the wings for their intro to the tar. All in all, no issues, and it looks like the difference between the older and newer models is a maximum of 2mm.
