Funny thing – I was coming back to the site to add Daniel Lieberman’s comment about hard surfaces and saw your comment. I also qualified my statement a little more for clarification. I was referring to those who may have exisiting, chronic joint pain who may benefit from a more compliant surface. I’m not so sure about running on concrete or asphalt over a long period of time though. Now that we have a body of quantifiable evidence that a runner’s gait affects impact force with the surface, it would be interesting to see the results of a long-term study regarding hard surfaces vs proper running gait. Then we can dispell any confusion about injury risk as it relates to running surfaces.

On the contrary, as Lieberman’s research shows, if you’re running barefoot-style, the hardness of the surface you’re running on is irrelevant. Lieberman specifically says that you can run across steel with no ill effects.

Smooth surfaces like concrete and asphalt are the easiest surfaces for barefoot-style running. If you want a problem surface, go try a trail full of rocks or acorns. I can be done, but it’ll make you appreciate those smooth and easy concrete and asphalt roads a whole lot more!