Some breeds of dog are bred to run. A fine example is my Australian Working Kelpie, Guinness. He was raised on a sheep station, and those dogs are mustering sheep in the paddock from quite a young age. I started running with Guinness when he was just under 12 months old.
Some breeds have inherent orthopaedic problems, and in those breeds, I’d hold off a while until their body is more physically mature.
Smaller breeds of dog are physically mature before larger ones, so it’s safe to say you can start running with a Jack Russell Terrier before you can start running with a German Shepherd Dog.
Veterinarians recommend that growing pups and dogs don’t participate in “forced exercise”. That is basically any exercise that they wouldn’t participate in with dogs of the same age. One guideline to consider is that a 5-6 month old dog is physically comparable with an 8-10 year old child. How much forced exercise would you allow your pre-teen child?
I think it’s a matter of plain common sense. For most breeds, 12 months is a reasonable age to start a running program. Start gently, don’t run too often, and keep him on soft terrain such as grass and trails. Make sure you watch him, because a lot of dogs don’t want to stop when they should. It’s up to us to keep their enthusiasm in check.
Photograph of the gorgeous puppy by Normanack