mesomorph

mesomorph, a human somatotype (physical type) that is marked by greater than average muscular development, as determined by the since-discredited physique-classification system developed in the 1940s by American psychologist W.H. Sheldon. Sheldon linked mesomorphy to certain character traits—namely, being extroverted, active, and competitive—an idea that today is considered pseudoscience, unsupported by scientific evidence.

Although the Sheldon system of classification did not make absolute distinctions between types, a person was classed as a mesomorph if mesomorphy predominated over endomorphy and ectomorphy in his or her body build. The extreme mesomorph somatotype score was 1-7-1, with the second digit referring to mesomorphy and the other two to endomorphy and ectomorphy, respectively, on a scale of 1 to 7. By Sheldon’s physical classification, the extreme mesomorph had a square, massive head; a broad, muscular chest and shoulders; a large heart; heavily muscled arms and legs; and minimal body fat. Such an individual tended to develop muscle easily. His or her muscular development was distinguished from that of one who developed muscles through bodybuilding exercises.