Parkour is a physical activity that is difficult to categorize. It is often mis-categorized as a sport and an extreme sport; however, (1) parkour has no set of rules, team work, formal hierarchy, or competitiveness. Most experienced practitioners think of parkour a (2) discipline closer to martial arts. According to David Belle, "the physical aspect of parkour is going over all the obstacles in (3) your path as you would be in an emergence. You want to move m (4) such a way, with any movement, as to help you gain the most ground on someone or something, whether escaping from it or chasing toward it. " Thus, when faced with a hostile confrontation with a person, one will be able to speak, fight, or flee. As if martial arts (5) are a form of training for the fight, parkour is a form of training for the flight. Because of its uniquely nature, it is often said that parkour (6) is in its own category. A characteristic of parkour is efficiency. Practitioners move not only as rapidly as they can, but also in the most direct and effective way (7) possible; a characteristic that distinguishes from the similar practice (8) of free running, which places more emphasis in freedom of movement, (9) such as acrobatics. Efficiency also involves avoid injuries, short and (10) long-term, part of why parkour’s unofficial motto is to be and to last.