Anatomical posing tips
Hiya everybody, Alonso here.
Thought I'd mention a couple of anatomy facts that might help to make your poses a little more believable (if you're going for believable).
It's physically impossible to lift your arm higher then horizontal without also raising your shoulder. (This is because there's a little ridge on your upper arm bone (humerus) that connects to your shoulder blade at horizontal and pushes it up when you go higher)
There's a tendon in your pelvis that tilts your pelvis forwards when you try and reach behind you with your leg.
In a non cartoon human, the rib cage is a fairly solid structure so any bending and twisting is usually happening in the lower back, the neck, and in the shoulders. (so don't try to bend the rib cage in half, bend as far as you can with shoulders and stomach and neck.) So make your line of action, but then be aware of where the flexibility comes in when fleshing out the anatomy on top of the line of action. (The shoulders are super bendy, so they often disguise how stiff the rip cage is, because they cover the top part of it)
hope that's useful to some of you. :)
(sorry for my weak tablet drawings, but it's easier to jot out a sketch then find a suitable copywrite free image, so don't trust my crappy drawings stand up and test this stuff out on your own body, or do an image search for yoga and draw on top of it)
Aug '09 Oh, update! check the comments to see what my mom has to say :)
Ian Here - I like this post so much I'm adding it as a resource to the character posing section, thanks Alonso