This over-50 extreme sports athlete makes peoples' jaws drop with only one wheel. Terry Peterson, best known as the UniGeezer, has become a worldwide sensation on a unicycle.

It's the ultimate motorized highwire act, requiring lightning-fast reflexes, incredible strength and stamina, and nerves of steel. For decades, motocross has been a young man's extreme sport. It's still extreme, but suddenly there's gray hair everywhere.