It doesn't work sitting down (well not for me).
On your feet soldier!
Raise your shoulders into a shrug and let them drop down fast.
Did you get a tingling feeling in your hand?
If you did then you could have hunched shoulders. This is only a theory I just came up with.
Now try the same thing but with your shoulders back a bit. Doesn't do it like that does it?
p.s. Played footie today and got some injuries where I was thinking "That really should hurt". Isn't
Test a wonderful thing, and I'm not adding any. Feet were killing me though.