We've all heard some type of medical myth. Some people believe them, others don't.

So you have to sneeze... It can sometimes be annoying, but can it stop your heart? MCG physician Ramon Parrish explains.

"Sneezing occurs in a time period that's much less than a heartbeat. So does it do that, no," Parrish said.

So what about those knuckles? Does cracking them cause arthritis?

"It's one of those that there's some truth to it, some not. Over a long period of time, if you crack your knuckles, you can have damage to your joints," Parrish said.

A not so funny myth, tickling yourself. Why can't we do it?

"If you try to tickle yourself, you inhibit those neurons that enable you to create your own laughter. It's one of those things you just can't do to yourself that somebody can do to you very easily," Parrish said.

And finally, a myth that shouldn't be too tough to swallow. Does gum stay in your stomach for seven years?

"All things swallowed that aren't digested eventually come out and there's no exception to that, even with chewing gum," Parrish said.

Doctor Parrish also says yawning is contagious, so be careful.