Pelvic Rotation Effect on Human Stride Length: Releasing the Constraint of Obstetric Selection

As human walking speed increases, pelvic step accounts for a greater percentage of total step length and is associated with an increase in amplitude of pelvic rotation. As a result, for any given speed individuals of varied pelvic width and leg length should differ in locomotor kinematics and energetic cost. Yet despite absolutely shorter legs and wider pelves relative to leg length in females, mass-specific cost of transport in walking does not differ by sex. Focusing on stride length as the major component of gait economy, we perform a quantitative analysis of temporal, spatial and rotational gait parameters using kinematic measurements obtained from 30 healthy adults walking at two comfortable speeds. We predicted that a larger component of stride length would derive from pelvic rotation in females and that a stride length model incorporating pelvic and limb kinematics would be a better predictor than a simple limb-based model. We found that pelvic rotation was greater in females at both speeds but reached significance only at the faster speed. A larger component of female stride length derived from pelvic rotation and the female hip translated farther than the male hip, but only when walking faster. The Model_{LIMB and PELVIS} was a better predictor of stride length than the limb only model and accurately predicted female stride length but not male stride length. Females exploit the breadth of their obstetric pelvis to obtain longer strides relative to leg length and perform at comfortable travel speeds with greater excursion angles than males. Anat Rec, 300:752-763, 2017. © 2017 Wiley Periodicals, Inc.