Factor analysis and somatotyping, are these two physique classification methods comparable?

The aim of this study was to investigate the correspondence of physique structures estimated by the Heath-Carter anthropometric somatotyping method and a factor analysis based on the same set of 10 variables used by Heath-Carter. The investigation was carried out on a group of 200 healthy young adults of 20 years of age who were students of physical education. The mean somatotype was 2.7-4.6-3.0 for the males and 3.3-3.4-3.1 for the females. The 73% of the total variance in males and 75% in females were represented by three factors. They were identified as muscular, fatness and skeletal factors in the males, and in the females as muscular-trunk fatness, skeletal and limb fatness factors. A PCA gives different results depending on the measurements used for the calculation. The same set of variables as for the somatotyping method were used intentionally to extract the PCA factors and to evaluate the possible correspondence between these factors and the Heath-Carter components. On the basis of the correlation between the factors and the somatotype components, one can conclude that there is: (1) a high correspondence between endomorphy and fatness factors in both sexes; (2) that mesomorphy correlated positively with the muscular factor in males and negatively with the skeletal factor in both sexes; and (3) that ectomorphy was highly positively correlated with the skeletal factor and negatively with the other two factors in both sexes. Factors and somatotype components do not correspond exactly which leads to the following conclusions: (1) The three somatotype components cannot be identified as orthogonal factors in a factorial analysis based on the same measurements as for the somatotype, e.g. the ectomorphy component is not an independent factor in males or in females; (2) The muscle measurements and bone width used to estimate mesomorphy in somatotyping scored in two independent factors; and (3) The factor structure of the 10 measurements was sex dependent.