STORY: Gueorguiev said that he would be locked in the glass box for 15 days, only communicating with the outside world for 30 minutes each day.

The athlete, who has run some 30 ultra-marathons worldwide, said described the experiment as "psychological".

He said he loves his privacy and that it will be "quite challenging" to have people looking at him "24/7".

The funds raised will be used for various projects to prevent addictions among children under 18, including drugs, alcohol, digital media and energy drinks.