Proper form is key when performing a workout to guard yourself from injury. But even with meticulous form, things can still go bad. And throw in the wildcard of Crossfit, and sometimes things can go wrong.
This dude is performing with a crazy Crossfit workout or is training for the horizontal bar in the Olympics when things go wrong during the dismount.
Dude is spinning backwards in the air when the back of his head meets the bar. The sound is so loud I would not be surprised if there is a fracture on his skull. He seems to walk away but I hope he gets looked at by a doctor.