Construction Drawings

I have been trying to pay attention the last few days to where I place the origin of the legs so that they lie within as opposed to below.

Also, I have been itching to do some drawings of the geometric locking of the knees elbows, and such. I should do so. I am not quite getting what you are saying about the circle to outline the upper part of the leg cylinder.

I really need to learn the names, and that will help me distinguish and differentiate them. I am aware that my knowledge of the upper back and down to the glute muscles is lacking in development. 

I suppose in real life my back muscles could use a bit more development, but that's a different matter... ha, ha! Need to get out of the office chair...