I've been running in Adrenaline's for years and have always loved them. Prior aches and pains in Nike Zoom's disappeared after switching to Brook's Adrenaline 12 and I never looked back, always continuing on when new releases came out. With that being said, I'm super disappointed in the 15's. They hurt after the first couple miles and put a bruise on the top of my foot that stayed for a week. They are stiff and unyielding. I'm so disappointed! Never again.