This question always comes to mind whenever I see people jogging along sidewalks, and wonder. Sidewalks are generally concrete or cement or something, which is definitely harder than dirt, so…
This question always comes to mind whenever I see people jogging along sidewalks, and wonder. Sidewalks are generally concrete or cement or something, which is definitely harder than dirt, so…
There was a mini scandal at the Atlanta Olympics because they made the track surface very hard, to suit sprinters and long-jumpers (in the hope of new records, in sports where the US is strong) and it meant that some of the runners who usually do the 5k and the 10k (track) struggled to compete in both events. (The sprinters, of course, were not covering enough distance to care.)
I managed to track down a decent reference for it, which also addresses your question in some detail: The Hard and Soft of It
But comparing trail to road is a bit more complicated. Trails can be pretty hard and also, not as smooth and even as (some) roads, and asphalt is different from concrete. The linked article has some good discussion of different surfaces.