In the first one, lots of form in the back lost in the shading, The roundness of the rib cage leaning back seems flattened by the lines of your shading. The furrow created at the tendon of the latisimus that curve around to the obliques seems like just a simple small crease line, the overall height of the figure is foreshortened indicating a large backward lean, but the anatomy doesn't show it well.  The second one indicates that you seem to be in a rush. Try to ask yourself what part you're trying to draw and where does it jut off to in 3D space, this is a lot easier than it sounds if you use the proko anatomy course, or even the free proko anatomy videos on here and on youtube. It may help to always position your drawings so that they force you to draw at least one thing in perspective, that isn't just a flat plane with a relief on it. In the first drawing you seem to want your character to be leaning, like a figure skater and for the legs to be posed with some depth with one behind the other, but realize that your butt and pelvis is too static for the legs to do that. I made a little corrective drawing. I know this is 11 months old.