Due to the ridiculous amount of heat and humidity in San Antonio I haven't been able to run with Sancho. My husband took him to my aunts house where he played indoors for about 3 hours with her dog. We then took him to the park for a run. He seemed fine in the beginning. About 30 minutes into it he started to drag his hind legs. He has never done this. We carried him to the car and by the time we arrived home he was fine. I really thought he pulled something but he is perfectly fine now. Can dogs get leg cramps? Could there be another explanation?