One of the threads lately got a little sidetracked into exercise for young dogs, and I think the consensus was not more than 1 minutes per week of age , up to one hour/1 year old. But that was just walking, not running. Hopefully whoever posted that will catch this and correct me if my memory is faulty.
Personally I will not run my dogs until they are over a year, other than what little trotting they do for heeling work in training class and home workouts. Everything I have read stressed keeping strain off of those developing joints.
Stella