To create biomechanical models of five common coital positions, and evaluate the degree of contact and forces against the clitoris. To evaluate clitoral blood flow before and after engaging in these positions.

Biomechanical models were rendered of a male and female pelvis in the following coital positions: face-to-face/female above, sitting/face-to-face, face-to-face/male above (with and without pillow), and kneeling/rear entry. The thrusting force and gravitational force were estimated for the pelvis(es) providing the main forces. The areas of contact between the pelvises were identified and highlighted. Sonography of the clitoris was performed before and after a healthy volunteer couple engaged in each position, using a Philips Lumify™ ultrasound (Koninklijke Philips N.V., Amsterdam, Netherlands) with a L12-4 linear array transducer (4–12MHz).

The biomechanical models for each position, with the exception of kneeling/rear entry, reveal a large amount of contact with the clitoris. Clitoral blood flow increased after engaging in each position except for kneeling/rear entry. Positions in which the gravitational force of the thrusting partner was in the same direction of (and thereby augmenting) the thrusting force resulted in intense clitoral blood flow (face-to-face/female above, and face-to-face/male above). Augmenting the face-to-face/male above position with a pillow generated a component of the male pelvic gravitational force in the direction of the clitoris; this resulted in more blood flow to all components of the cavernous body.

From a biomechanical perspective, different coital positions vary in their potential to stimulate the clitoris. These positions lead to variable increases in clitoral blood flow, concordant with our biomechanical models.