44.1 Thursday, Jan. 5 Effect of Pelvic Rotation on Stride Length: Redefining the Human Obstetrical Dilemma WHITCOME, K.K.*; O'CONNOR, J.P.; LOPEZ, J.; MILLER, E.E.; BURNS, J.L.; University of Cincinnati, Cincinnati; Harvard University, Cambridge; University of Cincinnati, Cincinnati; University of Cincinnati, Cincinnati; University of Cincinnati, Cincinnati firstname.lastname@example.org
Human males and females differ in skeletal shape and size, notably within the pelvis. The correlates of this sexual dimorphism are known with respect to obstetric function but consequence in locomotor performance is less well understood. Given that a relatively wide pelvis generates more gravitational torque during swing phase than a narrow pelvis, we ask do pelvic determinants of gait differ by sex, and if so, do sexes achieve similar locomotor results in terms of gait economy? Here, we introduce a new pelvic rotation model to determine sex-specific effects of pelvic axial rotation on stride length. We examined locomotor kinematics in a group of 30 adults within which sexes differed anatomically in mean body mass (male 77.3 kg [1.8], female 60.8 kg [1.7]) and mean pelvic width (male 262.8 mm [3.4], female 258.9 mm [4.3]). Females have a greater dimensionless stride length at slower and higher speeds (1.57 [.07], 1.92 [.02]) than males (1.46 [.08], 1.82 [.01] and have larger excursion angles of the pelvis in the transverse plane (38.3 [13.1], 47.0 [12.2]) than males (47.7 [8.3], 53.6 [3.6]). Incorporating the kinematics into a biomechanical model combining limb and pelvic dynamics showed that females generate greater forward hip translation than males (P<0.0006). Further, the new model is a better predictor of stride length than a simple limb-based model and accurately predicted female stride length (P=0.362) but not male stride length (P<0.0000). These findings suggest that despite high hip torque emphasized by the Obstetrical Dilemma Hypothesis, females uniquely exploit the translational effects of the relatively wide pelves to increase stride length. Research supported by the University of Cincinnati.