A perhaps workable fuck-ton of running references (per request).
[From various sources.]
(….. There is no rational reason for it to be this bloody difficult to find human running references…….) Just recognize that there are a few different kinds of running. The torso can be hunched over or upright. Understand the weight distributions and what happens if suddenly stopped. (I don’t know as much about running as I ought to… I would suggest looking up “how to run” tutorials on YouTube.) O! And a common mistake is to make the front leg straight; DON’T DO THAT. The front leg, even when extending, is bent! The only time it’s straight (like in the green GIF) is when the body is rising high enough off the ground to allow the leg to fully extend.
[And, allow me to clarify some of the comments that’ve shown up on this particular post: The first image IS accurate. The figure isn’t moving up and down because it’s going incredibly fast. The faster you go, the less you bob vertically. The Quinto/Cumberbatch GIFs are great examples of that. Also, yes, if you’re going for practicality, the faster you run, the more of an angle you’ll stoop to. But, mind you, the Star Trek GIFs are from a movie. It would not be fashionable to be hunched over. They’re running aesthetically, not practically.]