In the early 1920s, Marie Stopes claimed that when wearing a diaphragm, the vagina is stretched such that certain movements made by the woman for the benefit of the man were restricted by the diaphragm spring. In later years there was some discussion of this, with two authors supporting this concept and one opposed. One of them argued in the later 1920s-1930s that while the muscle movement by women is restricted it does not make all that much difference since most "women (in the 1920s) are not able to operate their pelvic muscles voluntarily to the best advantage" (during sex). However, Stopes anticipated this rebuttal, and in so many words classified it as a lame excuse.