Growth patterns and physical plasticity in adolescent laborers

Data about the effects of working environment and excessive physical loads on human growth and constitution are insufficient. Although there are a few studies which link growth retardation in children's stature and long bones to their exposure to hard labor, it is difficult to discern whether the detrimental effects of compressive forces on growth result solely from severe compressive stresses or from the subjects' poor economic and substandard nutritional conditions as well. The aim of this study was to clarify this issue by comparing the anthropometric dimensions of laboring and non-laboring adolescents; both groups came from lower socioeconomic strata and were subject to poor living conditions. The laboring group consisted of 532 male apprentices aged 13.5-18.5, and the control group, of their 451 non-laboring peers who were attending school during the period of observation. Body weight, 3 vertical dimensions (stature, upper and lower limb lengths), 2 diameters (elbow and knee breadths), and 3 circumferences (contracted and relaxed upper arm girth and calf girth) were measured. In addition, relative growth according to the body height for each variable was computed, since relative variables are more valuable in evaluating the effects of excessive loading on the human body. The analyses showed that all vertical dimensions of laboring adolescents lagged behind those of their non-laboring peers. There were also clear differences between the two groups with regard to relative diameters and girths. The pressure effects of physical activity stimulate the transversal growth of the long bones. Similarly, circumferences, especially contracted upper arm girth relative to stature, are more developed in the laboring group than in the non-laboring group. These findings suggest that excessive workloads retard adolescents' vertical growth, especially in upper parts of the body, but that they stimulate transversal growth of the long bones and muscle development.