Paddy and Lola ( my staff and GSD pup ) play rough and I too make sure they know when i say enough, its time for them to stop. Lola has specialised the leg technique and fights smart but paddy generally just uses his strength to get the upper hand - both have had minor scratches - but take turns initiate the next bout so I know they both enjoy it - and as long as they know I decide when to cool off I think its a good way for two young hearted dogs to let off steam.