A lot of women, even some who are fairly slender, seem to have grooves permanently worn into their shoulders by their bra straps.
It has made me wonder:
1) Is it just something that happens just because you wear a bra all day, every day? And if so, how long does it take before you develop permanent grooves?
2) Is it something uniquely female based upon softer tissue in the shoulder area?
3) Is it because they wear their bra straps too tight?