Hi, I have a GSD pup who is 7 months old now (bitch) and i have a 4 year old gremlin. I have to be honest from the get go i never let her get rough and she was never allowed to play fight with me or even do it near me. Thankfully my 4 year old does like to play but even in his small size he knows how to put her right. If i am there i always assume control of the situation and them both. Now it tends to be the bitch on the floor with my gremlin on top pinning her down. It is quite funny to watch. I even let Kirah sometimes play with the cat which just shows how soft she is now. You just need to show the dog that you are the leader. If you get any situation like that again i think it is best if you pin the dog to the floor making it submit (as a pack leader dog would do).
Make sure you are always coming into the house before the dog, eat before the dog, correct the dog at any sign of mistake and even ah ah the dog if he shows any sign of going to play fight roughly.

Oh and on the side of exercising ...
Oh i can't wait for the responses to this but my GSD has been on walks for 3 hours ... WAIT FOR IT!!!
She does get rests. SO i don't mind. If she was running around like a lunatic all the time then i wouldn't be so happy.
She usually gets a 30min walk in the morning and then usually a 1.5-2 hour walk in the afternoon. BUT i have a little boy who comes out obviously and he walks very slow as little ones do. My dog will lie down and have rests whilst he blows dandelions. Really it is totally up to you. If your GSD will run around like a lunatic throughout the entire walk i'd say stick with shorter walks with balls. If your dog will rest or you have slow walks or anything then yeah longer walks are alright. On a website like this you will get a gazillion bits of advice, you will get haters but you know your dog, what personality your dog has and you have to make a judgement on that

If you get any situation like that again i think it is best if you pin the dog to the floor making it submit (as a pack leader dog would do).

Interesting advice however............

pack leaders do not actually pin dogs to the floor making them submit

this could be potentially dangerous

therefore this outmoded, discredited and illadvised practice is not to be encouraged.

Oh i can't wait for the responses to this but my GSD has been on walks for 3 hours ... WAIT FOR IT!!!
She does get rests. SO i don't mind

Again very poor advice which no GSD breed club or breeder would endorse.

You would not take a 3 year old out for 3 hours walking and this is the equivalent.

If you would like to minimise the risk of HD, OCD, etc then, apart from buying puppies from reputable breeders who conduct all the necessary health checks on their breeding stock, you have a duty of care to ensure that you minimise the environmental factors in musculo skeletal disorders.

If you as an owner do not mind, I think the dog may do, and of course puppies, like children, do not know what is best for them.

know this is going to sound stupid but what exactly IS body slamming?x

Several breeds do this, but it appears to be a favourite technique of GSD.

Basically they like to keep their flock together, so if your other dog is at A and you are at B they will try to keep you in one place, and instead of the eye and stalk method of BCs a GSD will use their body to "persuade" the flock member to go somewhere else; they tend to use the side of their bodies to hit another dog.

Generally speaking many dogs do not appreciate this and of course it can be potentially harmful to the other dog.

I knew straight away someone would pick up on that bit and that bit only, not the fact that she rests, lies down during the walk or anything else. Again i stress she is not walking or exercising for 2 hours.

A dominant dog would stand over or make another dog submit to show it's dominance and position in the chain. How you go about doing this is entirely up to you. I tell my dog down and she lies down, if she's done something wrong she will roll onto her side. This is sufficient enough for me.

Especially if you have a smaller dog who could get seriously hurt from a GSD doing this.
Gizmo is about 1/10 of Kirah's size, maybe smaller. It was something i worried about at first so i was quite strict with Kirah when i first got her. I think Kirah now thinks she's Gizmo's size and Gizmo hers

Oh dear <sigh>

Presumably you have to eat the same food as the dog too? Oh and, of course, when you pin down a large dog (with big teeth) make sure you are wearing the steel mesh gloves that butchers wear that go right up your arm so that you only get a bruise when the dog decides to bite and not the flesh ripped off your arm.

Even wolves, never mind dogs, don't do this in the wild, let alone dogs so what purpose, except to show that the dog has a slightly barmy owner, does it serve?

why is the dog biting the owner? Nice to know people can't have opinions or methods without being called slightly barmy.

As a matter of interest, when your dogs are let out last thing at night, when it is pouring with rain, do you go out of the doors first before your dogs?

I don't I like to stay in whee it is nice and warm and not get drenched in my pjs.

If my dog has to eat at a time when it is not convenient for me to eat, what should I do, pretend to eat?

There is no need to do any of these things, unless you happen to be a disciple of Jan Fennell, who believes that without this you cannot control your dogs.

Fortunately for the canine population, no reputable behaviourist follows the doctrine according to JF.

My dogs NEVER roll on their sides unless I give them the command.

And my dogs never know when they have done something "wrong" as they are amoral.