Does your trainer say this:

Does your trainer say this to you during a lesson: * I want to nail you to a cross to keep your shoulders open* haha She says we(me,my sister,and my mom)all ride with a slump ..so she wants to nail us to a cross.

Nope, that's never been an issue for me. Partly because my mother and grandmother always scolded me if I didn't walk with my shoulders back and chest out. Didn't like it back then, appreciate it now.