The knee-jerk reflex; What happens if you are clenching a book when your knee is struck?

Question

When your knee is hit in the tendon with a hammer, your leg jerks forward – but what happens if you are clenching an object (like a book) when your knee is hit?

Answer 1

Probably not much.. unless you really got clobbered.. then you might drop what you are holding..

Answer 2

haha i just tried that. and i read somewhere that you cant do the knee jerk thing. or tickle yourself. because your brain knows its coming and thoes reactions are caused by an element of surprize.. but i tried it anyway, and it didnt work, holding a book with my leg or not. i would assume it would be harder to get the knee jerk because you are clenching and perhaps expecting it. this would be a good science fair project.