the trail tougher than the sidewalk?

I do about 80% of my running during the week on concrete sidewalks. On Saturday, I do mostly sidewalk and pavement with maybe a mile on a trail. Sunday, including last Sunday, on a mostly firm dirt or fine crushed gravel trail. I swear I was more sore after Sunday's 13.6, which followed an easy 5-mile day, than I was after any of the 14-, 10-, or 12-mile runs I did back-to-back-back last Mo, Tu, and Wed. Well, anyway I thought I felt better after yesterdays 10 miler than before it and that proved to be true this morning when I did 13 on concrete sidewalks. No niggles today.

Today was also the first day in a while I had that "I can run forever" feeling. I think I'm beginning to turn the endurance corner. Runs of about 1 hour apiece are on the menu for the next three days.