Done within classmode

Seems you're at the point where you should focus a bit more on anatomy and shape design, you're structure, the 3-dimensionality, could be worked up more, so go for anatomy studies trying to capture the structure of the pose (it helps to focus on major parts only, for studies purposes, like, just leg muscles or just upper back) and take advantage of the muscles to drop some shape designs to better ready and give more awesomeness to the pics.

Nice sketches, the 2values + 1 half tone are working great here.

Greatest job on your range of forces on your anatomy poses, but I think that you're totally but definitely on the rightest track, but I feel that these bones and muscles could use a bit more loosening up in your drawing workouts. How would you like to please pick up any anatomy book you've got in your home and on your computer, but please do 5 minutes of 30 second arm bone warmups.

As a result, your understanding and control of the arm bone anatomy will be drawn less than stiffest but the most dynamic, energetic, but fluidest. For most details, look into the Morpho Anatomy series on Amazon.com or your local bookshop's art sections.

Hope these have been completely but totally useful.