Background. Knemometry is a non-invasive method of precisely determining short term changes in the lower leg length. This method is more frequently applied in many countries. Objective. The goal of this study was to evaluate the influence of physical activity on growth process in children aged between 8 – 10 years. Material. During 2 – years longitudinal study we measured 66 children group both sexes. The experimental group consisted of children who were active in gymnastics or swimming. The control group consisted of children not routinely engaged in sport activities. Methods. Knemometry measurements were collected every two weeks except on winter and summer holydays. Results. The highest growth dynamic was observed in control females (–x = 0,47 mm/week) and the lowest in the group of the female gymnasts (–x = 0,39 mm/week). There were no statistically significant differences in the average body height in children from the entire tested group. Conclusions. The main conclusion is that the intense and type of physical activity differ growth process of the lower leg in girls aged from 8 to 10 years.