This PDF link that mspennyloafer added to our useful sticky thread might help clarify/explain some if it for you. I think one of the other posts there had another link about if your have compression w/arm/shoulders down vs compression w/arm/shoulders up... I'll look for it. I though it was on this pdf unless I missed it when skimming for it.

http://www.coloradohandtherapy.net/files/43426966.pdf

ahh here is the one I was looking for -
http://www.watainc.org/uploads/pdfs/...to-loehrke.pdf