Parkour：In the strictest sense as defined by David Belle, Parkour is the art of moving through your environment as swiftly and effectively as possible using only the human body. More broadly it might be defined as the discipline of developing the physical and mental capacity of the human being while through training to overcome obstacles. In practice Parkour is essentially the same as L'art Du Deplacement and most Freerunning. The difference in name has to do with David Belle's focus specifically on the utility part of training.
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