On Sunday I ran 11 miles in an unfamiliar place, and I finished after dark, and I forgot my headlamp.

So for the last several miles, I was running in very dark conditions. 

 

I got home fine, no problems.  But my calves were really sore.  Normally I could easily run that distance on that terrain without being so sore.  It was only the darkness and my own tension that caused me to overwork my calves. 

 

So the moral of the story is, relax. 

 

I think many of us who come from one extreme: heel striking in shoes, have a tendency to go to another extreme: trying to run forward on our toes, and overworking our calves. 

actually Ed you are right, an hour or 2 after my first ever barefoot run (5k) today I notice my calves a bit tender, also overall the bottoms of my feet have that feeling of quite a work over, not sure how they will feel tomorrow for my planned 20k.

 

But anyway I remember as I was running to keep on the balls of my feet (moreso than usual), perhaps this is why the tender calves.