The long range goal of the exercise in pregnancy study has been and continues to be understanding the interaction between the physiological changes produced by pregnancy and those produced by weight-bearing sustained exercise. Pregnancy stimulates both mammary and uterine growth which results in increased mobility in response to forces of acceleration and deceleration. Weight-bearing exercise produces sudden, high intensity accelerative and decelerative forces with each foot strike. The combination of the two appears to be additive and the resultant increased motion can cause severe maternal discomfort as well as concern over potential fetal contra coup injury. Recently garment designers have developed several specific pieces of expensive exercise apparel which supposedly decrease breast and abdominal mobility and relieve discomfort. However, the only basis for these claims is testomonial hearsay. The purpose of this study is to examine this issue by testing the null hypothesis that the acceleration, deceleration and/or overall vertical motion of the breast and abdomen produced by running and/or step aerobics in late pregnancy (32-36 weeks) is not reduced by 10% or more by wearing one of these garments.