I have a super dog who obviously enjoys her training with me (obedience) - BUT she only seems able to maintain her enthusiam for short periods!  She then seems to switch off and not co-operate. I know she knows the execises and my Trainer as said that she is capable of competing.  She prances in her heelwork (friends have said she looks smashing and clearly loves it) then suddenly will get over excited and leap up at me for her toy, if I try to ignore or encourage her to continue she goes all stupid like she knows nothing and as at times jumped up at me and grabbed my arm - a little bruised at times!!!  How can I help her to stay attentive and keep that spark without her going silly or even a bit stroppy?

H E L P

how old is she?
what breed is she?
what is she motivated by?

So you have not yet trained in duration............?

If she is switching off and losing her enthusiasm you need to remotivate her.  If the dog does not want to engage you cannot MAKE her.........  she has to WANT to.

If your dog is jumping up to get the toy then it sounds as though she is undertrained and if she cannot maintain the level of concentration needed in a competition environment in a familiar setting you will have no chance of getting it with the added distractions etc.

Do you clicker train?

Are you consistent in your training? if you cannot practise consistency yourself you cannot expect it from your dog?

Perhaps you need another trainer if you are seeking help elsewhere?