Why do ninjas run with their hands at the back? Ninjas in Naruto run with their hands at the back,

which is very different from normal anime character running.

Why is that? Is it because of their too much running speed or the wind force that their arms tend to be at their backs? Don't they lose balance when they run like that? Is there any explanation for this?
Based on research...
...Ninjas frequently were portrayed running with The Airplane Arms.


  Ninja are also frequently portrayed running this way (with the arms swept farther back, like the wings on an F-14 Tomcat), though they now tend to prefer the Ninja Run. Samurai also run in a similar manner, usually while keeping one hand grasped onto their katana. In a more (apparently) realistic series this may have something to do with the runner having a reduced profile and thus being harder to hit with ranged weaponry, but it's generally just the Rule Of Cool.


Emphasis by me.