I would wait for them to be fully developed. As with any breed, it all depends on their conformation. I would have your vet evaluate the dog before instituting any kind of running program with your pet. We own several mastiffs, our male runs the 40 acres we live on daily. He is always running, to the tune of 2-6 miles daily, our females on the other hand only occasionally run. Just as with anything, the conformation, temperament and build will dictate the runner.
Answered by fourpointsranch - 12/4/2012 11:21:20 AM