Many teenagers around the world are liable to display signs of rebelliousness and similar sentiments. Then there is Kerim Ahmetspahic. It's unclear if the 16-year-old is stubborn, but he is certainly hard-headed.
The Bosnian black belt in taekwondo recently set a Guinness World Record by smashing 111 concrete blocks in 35 seconds -- with his skull.
Ahmetspahic pulled off the feat by stacking the hefty slabs into 16 columns and acrobatically front-flipping over each one, head-butting them to pieces in the process.
A throng of onlookers, including a Guinness Book of World Records delegation, cheered and documented the performance inside a gym in the city of Visoko. The crowd erupted in celebration as Ahmetspahic reached the end of the line.
Just thinking about the record could make anyone's head hurt -- anyone, that is, except Ahmetspahic.