Ouch.

This morning, between 1.5 and 2 miles, my left calf muscle tightened up. All at once, and not a gradual thing, partway up a long gradual uphill, it just didn't want to go any farther. I had to stop and stretch, and then walk for a bit, and it loosened up enough to start jogging again. I finished 3 miles at a slow jog, and I don't even want to know how long it took me to get back.