In the frame of ELSPAC study ( The European Longitudinal Study of Pregnancy and Childhood) there was made an assessment of physical fitness of eleven years old children. Investigations used Brouha step test and also other characteristics were recorded. Influence of physical condition to the blood pressure and pulse was investigated, as well as the association of physical fitness with anthropometric parametres (BMI). Our study assessed also influence of physical activities to certain characteristics, for example we observed occurence of severe posture abnormalities in children who go in for sports on professional level. We cannot avoid positive influence of adequate sport activities to both psychic and physical development of the child. We therefore prepared recommendation for parents touching the selection of suitable sport activities and diet of the child who go in for sports.