Alright haha. No I never force run him. Though I have seen a couple of people in my complex who are running with their GSD puppies younger than Zeus! I feel so bad.
as long as it's not forced running (ie: him on a leash and you jogging him) and it's something where he can stop when he's tired, it's fine. At least that's what I always did, my dog stops playing and lays down after she needs a rest