Principal component analysis of shape variables in adult individuals

Human body shape variables were obtained by adjusting 34 distances between trunk/limbs, and head/face, landmarks, for an overall appropriate body size measurement. The adjustment was based on regression analysis. Principal component analysis was applied to thus defined shape variables to obtain shape dimensions in 99 normal adult males and 103 females. The first principal component either for trunk/limbs shape variables, or for head/face variables (considered separately in the analyses) is similar in both sexes in that it represents relative proportions between trunk and limb lengths and widths, and between midfacial lengths and widths, respectively. However there are appreciable differences in the succeeding components. The problem of interpretation of body shape dimensions, especially those accounting for less than 20% of the sample variance, as well as difficulties in assessing the biological meaning of dependence structures determined by principal component analysis in humans, are discussed.