William Herbert Sheldon (1898-1977) was an American psychologist and physician. He introduced the concept and word ‘somatotype’ in his book ‘The Varieties of Human Physique’ (1940). He defined somatotype as ‘quantification of three primary components determining the morphological structure of an individual expressed as a series of three numerals, the first referring to endomorphy, the second to mesomorphy, and the third to ectomorphy’. The conceptual approach is based on the premise that continuous variation occurs in the distribution of physique and thus the variation is related to differential contributions of three specific components, named on the basis of three embryonic germ layers:
- Endomorphy: It is characterised by the predominance of the digestive organs and softness and roundness of contours throughout the body. In other words, with increased fat storage, a wide waist and a large bone structure. Endomorphs are referred to as fat.
- Mesomorphy: It is characterised by the predominance of muscle and bone, skin is made thick by heavy connective tissue. The physique is normally heavy, hard and rectangular in outline. In other words, with medium bones and solid torso, low fat levels, wide shoulders with a narrow waist. Mesomorphs are referred to as muscular.
- Ectomorphy: It is characterised by linearity and fragility of build; with limited muscular development and predominance of surface area over body mass in other words, with long and thin muscles or limbs or low fat storage. Ectomorphs are referred to as slim.
The contribution of the three components defines an individual’s somatotype.
Method
Sheldon’s method of estimating somatotype utilises height and weight and three standardised photograph of front, side and rear views of the nude subjects i.e., 4000 college men standing before a calibrated grid. He summarized his photoscopic (he called it anthroposcopic) somatotype method as follows:
a) Calculation of height/³ √weight ratio (HWR) or reciprocal ponderal index
b) Calculation of ratios of 17 transverse measurements/diameters (taken from photographic negatives) to stature.
- 1) Four on head and neck
- 2) Three on the thoracic trunk
- 3) Three on the arms
- 4) Three on the abdominal trunk
- 5) Four on the legs
c) Inspection of the somatotype photograph, referring to a table of known somatotypes distributed against the criterion of HWR, comparing the photograph with a file of correctly somatotyped photographs, and recording the estimated somatotype.
d) Comparison of the 17 transverse measurements ratios with the range of scores for each ratio, to give final score
Each component of physique is assessed individually. Rating are based on a 7point scale, with 1 representing the least expression, 4 representing moderate expression and 7 representing the fullest expression of that particular component being assessed. The rating of each component determines the somatotype which is expressed by three numerals to sum of no less than 9 and no more than 12. The first number refers to endomorphy, second to mesomorphy and third to ectomorphy. Sheldon identified 76 different somatotype and most common are 3-4-4, 4-3-3 and 3-5-2.
The extreme somatotypes are:
1) Endomorphy
- a) Various parts of the body are soft and round
- b) Head is round
- c) Abdomen is flat
- d) Arms and legs are weak and fatty
- e) Upper arms and thighs are fatty
- f) Wrist and ankles are splendidly built
- g) Less linearity and less muscularity
- h) More fat deposition
- i) Somatotype rating is 7-1-1
2) Mesomorphy
- a) Bony and Muscular
- b) Heavy, coarse physique with rectangular contour
- c) Their head is massive and cubical
- d) Shoulder and chest broad
- e) Less fat and less linearity
- f) Somatotype rating is 1-7-1
3) Ectomorphy
- a) Typical characteristic is linearity
- b) Face is thin
- c) Forehead is high
- d) Chin is receding
- e) Chest and abdomen is thin and narrow
- f) Less fat and less muscularity
- g) Somatotype rating is 1-1-7
Criticism
- The somatotype changes: Sheldon stated that the somatotype is a trajectory along which an individual under average nutritional condition and absence of major illness is destined to travel. He used the word ‘morphophenotype’ to refer to the present physique and ‘morphogenetic’ to refer to genetically determined physique. He maintained that somatotype do not change throughout because it does not change significantly for any measurements except where the fat is deposited.
- Somatotype is not objective: Sheldon claimed that making measurements on photographs has raised the subjective technique to strictly scientific and objective level. He developed his own anthropometric method which depends upon soft part outline in the photograph more than osseous landmark.
- There are two, not three primary components, for endomorphy and ectomorphy are essentially the inverse of each other.
- Somatotyping omits the factor of size: In original method somatotype measured only body shape independent of body size.
- The method of somatotyping was developed on adult males. Criteria for defining somatotype components in children or females were not published.
- He used arbitrary scale that permitted no rating more than 7 or less than 1 in any component and their sum is limited by the numbers 9 and12.
Sheldon’s objective method
To meet these criticisms Sheldon described a ‘new’ Trunk Index method derived from the ratio of the areas of the thoracic and abdominal trunk measured on somatotype photograph.
- This index is assumed to be constant throughout life. It is possible that in the succession of the life phases the area ratio of thoracic trunk to abdominal trunk remains constant, that the two area increase and decrease in the size in relation to one another.
- He asserted that the new system provided a measure of massiveness (HWR), a separator for the kinds of mass into endomorphy and mesomorphy (The trunk index) and finally a measure of degree of stretching out into space (height). When the other two parameters are known, this is precisely what ectomorphy is.
- In this new method height was used as a measure of size, and substituted for ectomorphy.
- As a result of these changes, the sum of the somatotype components no longer need be limited to sum of 9 to 12 but now can extend to sums of 7 to 15.
- The original matrix of 76 somatotypes expanded to 88.The trunk index matrix gives 267.