Revista Brasileira de Educação Física e Esporte
Print version ISSN 1807-5509
SARANGA, Silvio et al. Sibling clustering in physical fitness: a study in Calanga, a rural region of Mozambique. Rev. bras. educ. fís. esporte (Impr.) [online]. 2010, vol.24, n.3, pp.363-372. ISSN 1807-5509. http://dx.doi.org/10.1590/S1807-55092010000300007.
This study has two aims: 1) to determine familial clustering in different physical fitness components and 2) to estimate its genetic component (h2). We sampled 330 subjects (174 males and 156 females) aged seven to 17 years, belonging to 132 families from Calanga, a rural locality in Mozambique. Physical fitness was assessed with the following tests: sit-and-reach (SR), standing long jump (SLJ), flexed arm hang (FHA), hand grip (HG), 1-mile run (1M), curl-ups (CU), and shuttle run 10 x 5 meters (SHR). Correlations were used to estimate sibling clustering, and genetic factors were computed using a variance components approach within a maximum likelihood framework. All computations were adjusted for height, weight, age, sex, age2, age3, sex*age, sex*age2 as well as a physical activity score. SAGE, a statistical package for Genetic Epidemiology, was used in all analysis.Correlations within each fitness component were low: brother-brother (between -0.01 and 0.25), sister-sister (between -0.19 and 0.45) and brother-sister (between -0.02 and 0.39). The genetic component in each fitness component was: SR h2 = 0.41 ± 0.16, p = 0.01; ALJ h2 = 0.60 ± 0.14, p = 0.001; FHA h2 = 0.18 ± 0.20, p = 0.37; CU h2 = 0.09 ± 0.13, p = 0.59; HG h2 = 0.19 ± 0.13, p = 0.16; SHR h2 = 0.07 ± 0.15, p = 0.63; 1M h2 = 0.49 ± 0.14, p = 0.001. Conclusions: 1) familial aggregation was higher between sisters than between brothers or siblings of opposite gender; 2) moderate genetic factors were found in flexibility, aerobic capacity and explosive strength; 3) variance between siblings in the other phenotypes were mostly explained by environmental factors that may be related to family subsistence activities.
Keywords : Epidemiological genetics; Siblings; Physical fitness; Mozambique.