Can be useful to run like the movies in Japan and the anime?
As you can see in some movies in Japan and anime including Naruto, ninjas are running with hands behind. Is this some sort of technical career or just to cool?
No, art is not a race … xD Maybe to relax too, but there is something behind it. Back then in ancient Japan, a ninja really thought you will run faster if the upper extremities should be clear and free of any work. =) Masashi Kishimoto is used make his characters as fully ninjas. Without it, people think of them as that … Samurai Warriors (some characters do not use Kunais but Senbon and swords so)