Running in Place (What is the best way to do this?)
 

Hey guys.

I'm very newbie to the film world and still trying a few test projects here and there. I was wondering what the best way to film someone to seem like they are basically always centered in the frame but running (from a side perspective). Is my only hope in a studio with a big continuous wall and my camera on a dolly?

thanks for any suggestions

Short answer:

Treadmill.

...in front of a green screen.

Would you take apart the treadmill arms? also for the background then how do you make it seem like he's going through the scene

Yes.
That's what the green screen is for, hence the suggestion. You shoot or acquire moving footage of the BG and then add it in, in place of the green screen, in post.

There are tons of machines to run on in fitness clubs.

Not many that are the same colour as the green screen, though.