jacks trembling legs

Question
I have noticed that in the warmer weather that when Max, my jack runs after the ball for a few minutes his whole body shakes, particular his rear legs and sometimes they give out from under him?  I asked the Vet but nothing came of it?  Is this normal?  He runs full speed but I am concerned.

Answer
My jacks do the same thing! Sometimes they are just sitting still and the legs tremble. If your vet isn't worried about it then I bet he's fine. As you know, they run so hard (and with such fervor!) and so fast, their muscles are overcompensating for the work-out they just went through. I bet his is excited and is probably anticipating when he can run again! If it changes or gets worse, your vet should re-confirm for you that it's OK.
I see this very often with many many jack russells.
Go Max!

Good luck!
Carol