I need some tips for gesture drawings?

[Marionew]

They can draw so quickly because they had thousand hours of practice and they draw it automatically. Search for simplified shapes in body spheres, cylinders, cones and draw them on your stickman figure. Sorry there's no shortcuts for it. You have to know anatomy and perspective to draw it correctly.

Wow, I was wondering how they were able to fill the stickman figure, so they used anatomy and perspective etc. Thanks for the tips, dude!
I know they had thousand hours of practice to draw it that well, just wondering how they fill it up, so where do I learn the anatomy to use it on my stick figure?