http://running.syr.edu/column/19980921.html
If your puppy likes to run around, it does not mean that it is ready for the rigors of long distance running. My resident veterinary expert provides the following guidelines:
Carefully choose your breed. All dogs are not created equal. The ideal running dog is medium-built, weighs 50 to 70 pounds, and has short light hair. Greyhounds and Labrador Retrievers are good runners. Avoid large dogs like Great Danes, and small dogs like Chihuahuas, since their body proportions do not favor distance running.
Avoid engineered breeds. The breathing system of Bulldogs is ill-developed and does not permit intense aerobic activity.
Respect the heat. Dogs do not sweat. They dissipate heat through their paws and mouths. Long-haired dogs like Chows and Collies have more difficulty in the heat. Plan your running route to allow drinking stops, and let the dog run through puddles.
Beware of genetic defects. Pure breeds like German Shepherds suffer debilitating inherited conditions such as hip displasia. Mixed breeds are less susceptible to hereditary problems.
Puppies should not run long distances. Wait until the dog is 2 years old to begin distance training. Start with half a mile every other day. Increase the distance by 10 percent each week. Give the dog a day off for every day of running.
Watch the paws carefully. Dogs do not have the luxury of carbon rubber outsoles. Check the paws before and after every run for any cuts or abrasions.
Run on a soft surface. The best running surfaces for dogs are grass fields and dirt trails. Concrete and hot asphalt impair a dog's ability to dissipate heat through the paws. At the other extreme, frozen roads, ice and salt are harmful to the paws.
Keep the dog on a leash when running on public roads and trails. It is safer for everyone, and it is the law in many communities. A 6-foot leash held to your waist by a belt keeps your hands free and gives the dog room to run around you.
Keep the dog visible to traffic. At night, use a reflective dog harness, a reflective tape the length of the leash, or flashing lights around the collar.
If you must run on roads, avoid busy traffic. The dog's head and nose are at the same height as automobile exhaust pipes.
Train your dog to obey you and ignore distractions. A simple jerk on the leash should bring the dog back to your left side.
Spay or neuter your dog. A dog in heat may spoil a good run.
Never enter a race with your dog. A road race is not a safe place for a dog. Many runners fear dogs, many dogs fear crowds, and starting guns startle dogs
