Hey,
I think there are a few things that could improve this:
- Add bounce to the guy. Usually the entire body moves up and down as a person runs. In yours, the head is not moving vertically and it makes him look a bit weightless. Usually, the torso and head are highest when the legs are most extended, and then it moves smoothly up and down
- Keep the arms bent at their most extreme point. Yours are straightening, and I've never seen someone run like that. They may decrease in angle due to the force of movement during the passing point (when they are both by his sides), but at the extremes they should remain bent.
- The leg straightens out as the body passes over it to push everything up, and the you push off with your toes. In yours, the leg remains bent after it lands, and then just lifts off the ground, there is no push
Other then that, looks good. It's quite smooth, just needs some hammering out to make it look weightful.