Spinning round holding a metal ball on a wire and then just letting go, what could go wrong.
Fun fact: The "hammer" is a metal ball on a wire and hasn't resembled an actual hammer since the 1800s.
Just swimming, cycling, and running back to back for people who decided one sport wasn't quite enough punishment.
Fun fact: The Ironman was born from a 1978 bar debate in Hawaii over which athletes were the fittest.