Hello, and good afternoon/evening.
Say, I must completely and totally adore your lighter touches of all of your quick sketches. Also, I love your choice of color theory in your figure rendering. Great sense of energy and electricity in the longer lines and liveliest, and largest edges. My smallest and insignificant improvement is that your forms and forces are a bit too rigid in terms of drawn appeal. How would you like to be on board for 30 minutes of 60 second quick poses, followed by 1 hour of 30 second quick poses? The reason why you could and should do this idea is as a result, your lines will become the least heaviest and inhuman, and the most dynamic, energetic, fluid, spontaneous, and liveliest in the poses. My hat's off to you, and I hope this piece of advice helps you out greatly. For even more info, be sure to check out an in-depth article 1, 2, 3, and 4. These about how much of the roughs are gutsier, and how the clean-ups are the polished. Cheers to you, again.