RESUMEN
BACKGROUND/OBJECTIVES: The study purpose was to assess the impact of birth weight and breastfeeding duration on physical fitness components. SUBJECTS/METHODS: Study participants were 985 adolescents boys and 1246 girls (12.5-17.5 years) participating in the HELENA study. Standardised physical fitness procedures included: cardio-respiratory fitness, flexibility, upper body muscular strength, and lower body explosive strength. Birth weight and breastfeeding duration were assessed by parents' questionnaire. Associations between neonatal data and physical fitness were investigated using linear mixed models. RESULTS: Significant associations between body muscular strength, and breastfeeding duration were observed in the unadjusted analyses for boys. When adjusting for potential confounding factors (z-score body mass index, fat-free mass, fat mass), only lower body muscular strength, by standing broad jump-a proxy measure of muscular explosivity- was positively associated with breastfeeding duration. Furthermore, significant associations were observed between upper body muscular strength (by hand grip),-a proxy measure of muscular power-in boys as well as in girls. CONCLUSIONS: Birth weight and breastfeeding duration have different effects on muscular strength components. The present results suggest that birth weight positively influences the development of muscular power, while breastfeeding duration positively influences muscular explosivity.