Allrighty dude, this is my first critique for this site, so Im going to try to do you solid.
You are doing things right by keeping your drawings loose and not being distracted by contours of the body. But the number one thing I think may help you is to reduce your lines.
Your line work is very sketchy and is most likelly the result of a common beginner mistake of "finding the line". You draw the line first, decide it isn't good enough, then draw it again ontop of it, again and again untill you get the line you want and this has two effects: it makes you lines bulky and harder to understand and it also takes up more time.
You need to be more confident in your strokes or else you entire piece will be a mangled mess at the end almost everytime, and you'll end up going over the lines you like over and over, which is why your five minute pose is so messy.
I know these mistakes cause I did them for a LONG time. A few things helped me fix them.
1. Before you make your first line, make the movement with your pencil or charcoal without touching the paper. Do it a few times until you are more confident in the line you'll make, then actually draw the line.
2. Try drawing with a thick pen. WIth a thick pen, you have to be confident in your strokes, and there is no fixing it once you make it. I had a brush tip pen that I used and the lines were to thick to go over again and again to try and fix. If the line wasn't curvy enough, I had to make do, and keep in mind how to do it correctly the next time. This is the more nuclear option, and it stressed me the heck out when I did it a couple times, but it did help.
3. Look up gesture drawing vids. These are always good no matter what level, and dont automatically stick with the first you tuber you find. There are a lot of different styles and skill levels and some will help you more than others.
You got the right idea with your drawings, dude! Keep it up! Once your first lines get more confident, you'll find youll have way more time to work on form and shading and junk.
your proportions are really good, but you should try focusing on working fast while adding as much detail as possible in the short time window provided. making your sketches smaller while practising can really help with that
Hey,Logged in because I saw some inproper advice given. Do not focus on details and do not try to move as fast as you can. I would say for now have 60 seconds be your shortest pose time and focus on the overall idea and basic shapes of the pose. Get the feeling and essence of the pose down in as few lines as possible.Take time to look at the figure and internalize how it feels and how you will draw it,like thinking out and approach in chess.As artist it is also our job to see less and get the idea/image across with as little as possible. I reccommend checking out the book "The natural way to draw" By: Kimon Nicolaides. He explains this perfectly and far better than any lesson i've ever had on gesture. Above all else the ability to relax and never give up is key.Hope that helps,friend.