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.
Objectives
Some previous studies suggest that humans do not conform to geometric similarity (isometry) in anthropometric dimensions of the upper and lower limbs. Researchers often rely on a single statistical approach to the study of scaling patterns, and it is unclear whether these methods produce similar results and are equally robust. This study used one bivariate and one multivariate method to examine how linear anthropometric dimensions scale in a sample of adult humans.
Materials and methods
Motion capture marker data from 104 adults of varying height and mass were used to calculate anthropometric dimensions. We analyzed scaling patterns in pooled and separate sexes with two methods: (1) bivariate log–log regression and (2) multivariate principal component analysis (PCA). We calculated 95% highest density/confidence intervals for each method and defined positive/negative allometry as estimates lying outside those intervals.
Results
Results identified isometric scaling of the upper arm, thigh, and shoulder, positive allometry of the forearm and shank, and negative allometry of the pelvis in the pooled sample using both statistical methods. Patterns of allometry in the pooled sample were similar between methods but differed in magnitude. Sex‐specific results differed in both pattern and magnitude between log–log regression and PCA. Only one measurement (shoulder width) departed from isometry in the sex‐specific log–log regressions.
Discussion
Our findings suggest that especially in sex‐specific analyses, the pattern and magnitude of allometry are sensitive to statistical methodology. When body mass was selected as the size variable, most human linear anthropometric dimensions in this sample scaled isometrically and were therefore geometrically similar within sexes.
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