These are not sprites. Sprites are those pixelated characters from video games. They must be in that pixelated style to be considered sprites.
As for these drawing, watch how people work. When you run, you never put that front leg straight out. It's always bent to some degree until it's starting the forward push. That forward push is the leg straightening out. The back leg bends as you bring it up front.
Also, watch your size on these pics. This is 4000 pixels, and that's so large that it takes forever to load.