The somatotype is defined based on the anthropometric characteristics of the subject. Sheldon (1940) was the first to introduce the concept of somatotype, identifying the presence in each individual of three distinct components:
 | ENDOMORPHIC (7, 1, 1) narrow shoulders and wide hips, soft body, high body fat, viscerotonic |
 | MESOMORPHIC (1, 7, 1) muscular, mature appearance, thick skin, correct posture, somatotonic |
 | ECTOMORPHIC (1, 1, 7) youthful appearance, tall, not very muscular, intelligent, cerebrotonic |
The morphological aspect can be defined by assigning a variable score from 1 (minimum) to 7 (maximum) to each of these three components.
The first digit indicates the endomorphic component, the second digit indicates the mesomorphic component and the third digit the ectomorphic component. In this way the number 247 indicates reduced endomorphic characteristics, mean mesomorphic and high ectomorphic characteristics.
Sheldon did not limit himself to studying the physical characteristics and associated each component also with certain psychic traits:
ENDOMORPHES (whimsical, youthful, expansive, tolerant, food-loving, sociable, in need of affection)
MESOMORFI (brave, confident, determined, lovers of adventure, risk and danger, eager for power, )
ECTOMORFI (introverted, reflective, clumsy, anxious, with an artistic soul)
SOMATOTYPE AND SPORT
Each of the three characteristics identified by Sheldon is necessary to excel in certain sports. For example, the ectomorphic component is essential in cross-country sports and high jump where body weight represents an important limit for performance. The mesomorphic component is characteristic of power sports, while the endomorphic component of contact sports such as sumo.
