Defining Extreme Sizes and Shapes for Body Armor and Load-Bearing Systems Design: Multivariate Analysis of U.S. Army Torso Dimensions

Percentile models commonly cited in materiel fitting requirements, such as 'fits the 5th through 95th percentile soldier, are inadequate definitions of the extremes in body sizes and shapes that must be fit to ensure the intended 90% accommodation of the Army user population. This report reviews shortcomings of the percentile methods in common use since the 1970s and applies multivariate statistical methods to the definition of extreme torso forms for load bearing and body armor design limit definitions. Principal Component Analysis (PCA) is applied to 12 torso dimensions from the U.S. Army Anthropometric Survey (ANSUR) database, and equal frequency ellipses (EFE) defining 90% accommodation are fit to plots of ANSUR subjects in the PCA space. Central and extreme forms for male only, female only, and male/female requirements are derived from the EFE equations and presented in tables for use by clothing designers and engineers whose torso clothing and equipment must meet '5th to 95th percentile' criteria. The study raises methodological issues and alternatives for follow up in future applied research.