I am curious to know what shoes you train in and why?
For speed work, Tiger paws, and Nike Streak XC. Because I like them. Treadmill runs: DS Racers. These wouldn't be my first choice of shoe now, but I can live with them. For training runs, I usually run in the
Mizuno precision -- because it's light, flexible, good "road feel", yet well cushioned. It also happens to be more "minimalist" than shoes that a lot of wannabe minimalists are wearing (such as high-heeled, posted "flats", or even posted trainers like the NB900)
But most importantly, the reason why I use what I use is -- why mess with what works ? Can you document just one benefit I would obtain from switching to flats for training runs ?
Once the body is trained to handle the activity one is putting on it the less important the surface becomes.
That's a nice theory, but I'm not going to blow my metatarsals in pursuit of the experiment I'd need to do to verify it.