tennis head

When you are sat on the sideline of a tennis match and a good rally gets going. Then you head begins to bounce from side to side keeping up with the play until you a) give up and rest or b) are finally relieved by the players.

"Morning Jane, I have woken up with an awful neck cramp."
"Well what do you expect John. You were watching Murray yesterday. You have tennis head!"

or

"I love watcching Roger Federer , he always gives me great Tennis Head!"