 The external contractile measure was the mean wave amplitude in mm at the lumenal surface. This metric was measured at the lumenal peaks and troughs only and was a measurement designed to study the relationship between endometrial wave activity, manifested as bulk motion of the uterus, versus internal contractile strength. The external contractile measure was reported in mmcontraction.The external contractile measure quantified the movement of the uterus as a whole as measured at the lumen, i.e. the motion of the uterus relative to the body. 