Problems arise from the shoulder straps of standard bras. Standard well-fitting bras are constructed in the form of a "square frame", with all dimensions adjusted for each woman in a normal standing position, with arms to the sides. When a woman performs an activity which requires her to lift her arms above the shoulders, the frame is strained because it is anchored by the chest band, putting direct pressure on the shoulder trapezius muscles. This may result in neck and shoulder pain, numbness and tingling in the arm and headaches. To avoid such problems the bra's shoulder straps are usually crossed at the back, or the bra is worn halter-style.