For me, surfaces make all the difference in how my legs feel. I live in a hilly urban area and my legs feel like crap after going for a fairly long easy run on sidewalks. Everything from my Achilles to my hips feels bruised the next morning. On the other hand, I can do a grueling workout in spikes at the track and my legs feel great the next. I can do workouts several days in a row if I stick to soft surfaces. Anyone else feel this way?