Secular change in muscular strength of indigenous rural youth 6–17 years in Oaxaca, southern Mexico: 1968–2000

Abstract

Objective: The study compared the grip strength of indigenous school youth 6–17 years of age in Oaxaca, southern Mexico, who were surveyed in 1968, 1978 and 2000.

Methods: Grip strength (Smedley/Stoelting) was measured to 0.5 kg in 1280 children and adolescent, 621 males and 659 females, in the three surveys. Height and weight were also measured. Strength of the right and left hands was summed to provide a general estimate of muscular strength. Summed grip strength was also expressed per unit body mass (kg/kg) and height (kg/m). Subjects were classified into four age groups: 6–8 years (childhood), 9–11 years (transition in adolescence), 12–14 years (early adolescence) and 15–17 years (later adolescence). Children 6–14 years were surveyed in 1968, 1978 and 2000 while adolescents 15–17 years were surveyed in 1978 and 2000. Sex-specific MANCOVAs were used for comparisons among years within age groups.

Results: Changes in grip strength between 1968 and 1978 among children 6–14 years were small and significant only in girls. Grip strength increased, on average, between 1978 and 2000 in boys 6–17 years but only in girls 6–14 years; adolescent girls 15–17 years in 1978 were stronger than those in 2000. Secular gains in muscular strength were generally proportional to secular gains in body weight and height.

Conclusion: The data demonstrate secular changes in muscular strength in indigenous rural youth in a community in the process of transition from subsistence level agriculture to an economy is less dependent upon agriculture.

Keywords::

• Secular trends
• children
• adolescents
• physical fitness
• functional capacity

Declaration of interest: The research upon which this study is based was supported in part by the Institute of Latin American Studies at the University of Texas at Austin and National Science Foundation grants BNS 78-10641, 1978-1980 and BCS 9816400, 1999–2002. The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.