Nice figures, just a couple suggestions
In your running figure your foreshortening of the legs is wrong. The size of your thighs suggest visually that the extending leg is behind the bent leg and no need to show the foot in the back (it looks flat).
It looks like your foreshortening is the biggest problem (which it is...I have troubles too!)
other than that, nice studies ..my favorite is the bottom right sitting woman
I miss my drawing classes