Free-runner Asid (real name Yusuf Yirtici) demonstrates free-running moves in London August 27, 2008. Freerun, is based on the theory of Parkour, using your body to get from A to B as quickly and efficiently as possible, but its practitioners place greater emphasis on individual expression, creative flow and artistic merit. Picture taken August 27, 2008. REUTERS/Luke MacGregor (BRITAIN)