Sexual Dimorphism at Different Stages of Ontogenesis Based on the Kraków – Longitudinal Growth Study, Poland

Abstract

Introduction and Study Aim 
The aim of the study is to assess the magnitude of changes in sexual dimorphism with respect to selected morphological traits and the results of physical fitness tests between the ages of 8 and 50. 
Material and Methods
The data come from the Kraków Longitudinal Growth Study and pertain to the somatic development and physical fitness of individuals born in 1970 and 1972, conducted in Kraków from 1976 and 1980 up to 2022. The Mollison Index was used to calculate sexual dimorphism. 
Results
The females were shorter, lighter and thinner than the males in all analysed age groups, and differed only with regard to body height in the 13-year-olds. They were characterised by lower stronger hand strength and lower limb explosiveness throughout the analysed period. With the exception of 8-year-olds, the females had smaller arm circumference, shoulder width and thigh circumference than the males at ages 32 and 50, and at age 17, the girls demonstrated larger thigh circumference. Up until adolescence, the girls had greater body fat under the scapula, on the triceps and in the abdomen compared to the boys. However, in both 32–34- and 50-year-olds, the men exhibited greater body fat under the scapula and in the abdomen. 
Conclusions
A high degree of sexual dimorphism occurs during developmental age – at the end of the adolescence period, especially for fat folds on the triceps and abdomen. Greater dimorphism is observed later, in early adulthood, i.e., at the age of 32–34 years, in terms of height and body weight, as well as body mass index, circumferences – of the arm and thigh, shoulder width, and performance test results. In adulthood (around the age of 50), a noticeable decrease in the degree of sexual dimorphism is observed, which results from the nature of involutional changes.