Even the most seemingly innocuous blow can trigger commotio cordis -- a hollow plastic bat, shadow boxing, a hiccup-remedying chest pat -- basically any contact at all. Statistically, commotio cordis is almost exclusive to male athletes below the age of 20, and usually occurs during sporting events. Here's a handy chart about precisely which sport is most likely to turn inexplicably lethal at any moment:
University of Connecticut
And, of course, the Sport Of Kings: "Try to dodge this tennis ball filled with coins."
Between 1996 and 2010, the Commotio Cordis Registry logged 224 cases. Though 10-20 new instances are registered every year, researchers believe numerous cases still go unrecorded. Its deadliness is mostly due to the fact that, should commotion cordis occur, you need a defibrillator to shock the heart back into action. For every minute of delay, the chance of survival drops 10 percent. So there you go: Just always have a defibrillator handy, any time you might need to give, or receive, a triumphant chest bump. Or, alternatively, never do anything that deserves a chest bump. You probably weren't going to anyway, but now you have an excuse.