last night I did 2 hours of the 3 hour trainer. It's not my first time using the site but first time in a month or so, figured I would make an account and share.
These are the results. I left out 2 drawings, one was in colored pencil and didn't turn out well at all, and the same for a Conte attempt. The first 2 images are regular 2B, then vine charcoal, pastel, and the last is charcoal again.
I think what's great about your drawings is that you have good proportions, but what I would suggest is to work more on your fluidity of your lines, and try not to pay much attention (within these drawings) to contour as much as gesture. Try not to sketch your lines with small strokes, but rather with one fluid motion. "Ghost" draw the form first to loosen your wrist and shoulder, and then in a few lines, lay out the action of the pose using "CSI" meaning... all of your lines should resemble these three letters.
If you ever get the chance, I recommend looking up Proko (Stan Prokopenko) on YouTube, or go to Proko.com. This guy has an amazing understanding of form and gesture, and has really good tutorials through YouTube.
My main recommendation is to try and draw everything in less strokes. Instead of multiple strokes (even back and forth motions) to draw the spine, try to draw the spine as one line, from A to B. It probably sounds silly, but it'll give your strokes more confidence and strength! :) It'll really make the motion pop out more.
Please let us know if you need more help. I will be around more frequently from here on.