I can see a lot of people who have problems with sketching things out on here. I'm not sure if this has been sudgested, but go to the 30 second drawing on posemaniacs.com. they flash a pose for a set amount of time while you try to sketch it out. then it automatically shows another randomly generated pose (out of the thousands of poses that you can study.)
The idea (as is the idea of this thread) to loosen up and draw more proportionate, and draw better. Here are some I drew with a 60 second time limit on each pose. It's a really good website, and it definetly helps your art. Make sure you read the directions, as well as the tips they have to give you.