Running
Running is a method of terrestrial locomotion allowing humans (and not only humans) to move rapidly on foot.
Some good
running photos:
,
and something classic from Eadweard Muybridge:
"Muybridge runner" by Original uploader was W mccall at en.wikipedia - Transferred from en.wikipedia; transferred to Commons by User:Naudefj using CommonsHelper.. Licensed under Public Domain via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Muybridge_runner.jpg#/media/File:Muybridge_runner.jpg.