Well, you purposefully didn't leave the hair completely static, and to me it looks a bit worse than if you had.
If you're going to have the hair move, then maybe don't have it change THAT much. (although maybe we can attribute that to shonen-style exaggeration
)
Right now, the changes in the hair are messy, and the
mass of the hair visibly
changes (take for example the first upward spike of hair, or the inside lines just below.
The right leg (his left) is obviously bulkier than the left one (his right). I would make the left one fatter
Maybe it would look better if his head went down slightly at the same time as it goes forward, and go up again when going backwards... (Although, maybe the change wouldn't be subtle enough in this resolution.)