In 1999, Dr. Pek Van Andel and colleagues, made the first MRI images of male and female sex organs while couples were having sex under, as it was put, cloistered conditions. MRI machines are said by some to be much like coffins.
In all, 13 experiments were performed with eight couples and three single women. The results, as stated in the journal: “The images obtained showed that during intercourse in the “missionary position” the penis has the shape of a boomerang and 1/3 of its length consists of the root of the penis. During female sexual arousal without intercourse the uterus was raised and the anterior vaginal wall lengthened. The size of the uterus did not increase during sexual arousal.”