Health-related Physical Fitness Of Portuguese Twins. A Quantitative Genetic Analysis

Abstract

PURPOSE: The purposes of this study were: (1) to evaluate familial aggregation in heterogeneity levels of physical fitness, and (2) to quantify the magnitude of genetic and environmental effects in different components of the Fitnessgram health-related physical fitness. METHODS: The sample comprises 231 twin pairs from different regions of Portugal of both zygosity (93 Monozygotic, and 138 Dizygotic) and was divided in two groups according to their age: group 1 (G1), from 5 to 11 years; group 2 (G2) from 12 to 19 years. Zygosity was assessed with 16 random DNA microsattelies using PCR amplification techniques. Physical fitness was evaluated with the Fitnessgram test battery, which included curl-ups (CU), push-ups (PU), trunk-lift (TL), one-mile run-walk (1M), and body mass index (BMI). Data analysis was done in SPSS 15, and SYSTAT 11. ANOVA models were used to estimate intraclass correlations (t) to compute heritability estimates (h2). RESULTS: Intra pair differences showed remarkable familial aggregation, because intraclass correlations were systematically greater in MZ twins as compared to DZ twins, showing a smaller intra-pair difference in MZ twins. In all fitness components, all t values in MZ in both groups varied from 0.72 to 0.90, whereas in DZ varied from 0.43 to 0.55. h2 estimates ranged from 0.75 (CU), 0.53 (PU), 0.63 (TL), 0.77 (1M) to 0.84 (BMI) in G1, and from 0.76 (CU), 0.59 (PU), 0.68 (TL), 0.65 (1M) to 0.81 (BMI) G2 showing very similar values in the two age groups. CONCLUSIONS: These results support the idea of familial aggregation in health-related physical fitness among twin pairs, and the importance of genetic factors in explaining interindividual differences. Genetic factors consistently explain from 50 to 80 % of the total variation. This calls for a more precise understanding of physical fitness levels of children and adolescents, the need to implement differential physical activity and sports programs to youth to meet the variation of their potential for change, as well as a careful interpretation of their response to such programs at the population level.