The far and near leg look like they have the exact same positions, just recoloured, which creates flicker. Make the positions a bit more unique for equivalent frames.
Also, who runs like that, really? It looks like he is powersweeping the floor or something. I have no clue where this turning the head while running thing came from, but it is bugging me to no end. Take a stick, go outside, run a bit and see how you would move. I doubt anything like this.
The actualy pixelart looks good tho.