Age and secular effects on muscular strength of indigenous rural adults in Oaxaca, Southern Mexico: 1978-2000

Abstract

Purpose: To evaluate age and secular changes in strength of rural Zapotec adults in Oaxaca between 1978 and 2000.

Methods: Grip strength, height and weight were measured in 1978 (n = 247, 19-82 years) and 2000 (n = 407, 19-89 years); 35 males and 52 females were measured in both years. MANCOVA was used for comparisons by age and year.

Results: Grip strength and strength/height decline with age; the slope is greater after 40-49 years. Both are significantly greater in 2000 compared to 1978 only in males 19-29 and 30-39 years and in females 30-39 years. Strength and strength/height decline at a slightly faster rate in females than males during young adulthood, but at similar rates in both sexes during middle age. Strength/mass is greater in 1978 than 2000, but differences are not significant in most age groups. Strength/mass declines linearly with age and rates do not differ between young and older adults of both sexes. Left grip strength/left mid-arm muscle circumference shows a pattern across age similar to strength/mass in both sexes.

Conclusion: Grip strength and strength per unit size declined with age. Strength and strength/height tended to increase between 1978 and 2000, while the opposite occurred for strength/weight. Results likely reflected in changes in habitual physical activity patterns associated with the transition from subsistence agriculture to less economic dependence upon agriculture.