Untitled

Good start! To reduce stiffness, one of the biggest things is to curve those action lines even more! The more you exaggerate the curve of the spine, the more dynamic and fluid it will appear. Don't worry too much about copying the exact curve of the photo reference you're looking at. Keep up the good work!

Exceptional job and atypical work, SINE, nonetheless, I've got one littler request: Why don't you go for loosening and refining you muscle memory on your next 10 minute figure chalk, pretty, pretty, pretty, pretty, pretty please, please, please, please, please????? Why?????? It's because you'll get you life poses will become your most feeling dynamic, energetic, solid, fluider, and liveliest. Totally suppose that it'll give you all the benefits.

Polyvios Animations

This is a great start! One thing that will definitely help with stiffness is to make sure your hand is relaxed as you sketch your construction lines in! Try taking a slightly gentler, lighter approach and see if you can put the same lines down, but only half as visible!

try to have more shapes that go in the figure for it to be easier to draw and outline it

i think these drawings are cute with the different circles and lines to interpret the human form! What style are you going for? I would add more straight edge lines and you'll get the curve of the human form. keep going, try new things with your sketches and get out of your comfort zone. Don't be scared but keep going! Good job!