In the bright lighted side, we could see the yamakasis, these stuntmen of cities in the luc Besson movie. In the shadowed side, there is parkour, that is also called the art of movement, and that most of the public doesn't know about, and it is understandable: these spider-men's reputation grew, and other young people wanted to practice. David and Sébastien share their passion with anybody who wants to know. The news is spreading: from neighbour cities of noisy and sarcelles, young people move to evry to learn the parkour. The rumour works well, and the show 'notre dame de Paris' offers them to go on a tour, but David and sébastien refuse: a two years tour across France would cut them from their base, and above all they don't want to abandon the other young people who need their help. Then luc besson comes up with a script for yamakasi. They refuse that too. The scenario presents them as revolted boys from housing estates who trick the police and use their skills to steal. Seb explains: 'us, that we don't want, it's to prostitute our art' chilling incorruptible ones. For how long? Seven of the newcomers - including David's cousin give in the temptation and play in the movie. They separate from the group of evry, and rename themselves the yamakasis (strong man, strong spirit). Once famous, they claim to have invented the Parkour, betraying the true parkourists. David, Seb and the others (Stéphane Vigroux, Yoann Vigroux, Jérome ben Aoues, Rudy Duong, Kazuma and Michael Ramdami) rename themselves the 'traceurs'. Irritated by this story, they tell me that: 'to anyone who want to learn the art of parkour, it's welcome, but for the media events, we reserve us the right to choose: now we know who come to train when there's a TV near, and who's really got the passion'. We understand them.