What breed of dog are you running with? I always worry about heat stroke. Dogs do not communicate well and you have to really watch them. Often, people do not realize that their dog is overheated until they collapse. Short nosed breeds are VERY susceptible to heat problems because the air isn't cooled enough before it gets to their brains.

I used to run 5 miles in the early winter mornings with my German Shepherd. Now, she is almost 14 years old & a three block walk is a big deal. I let her sniff all she wants these days! She doesn't see well and her hearing is going, but her sense of smell is still pretty good. She's also a little senile and has hip problems. But, she's a very happy girl! She spends her days on my bed, air conditioning going and a fan blowing right on her.