Work on feet part of the animation - the feet are chaotically changing their sizes during every step.
This time, you will have to put shading on an arm and a leg when they are moving backwards (this method is often used in anime, for ex.), that way you'll create a sense of volume in animation.
Ohhh there's also an area between the hips, under the body. It's a small line of emptiness between the legs. That area must become shorter/higher during every step, work on that, the hip movement.
StarksNotDead
Just don't stop, really