Background: The aim of the study was to define a change of physical effectiveness in a one-year training course and its relation with special effectiveness. Material and methods: The research was conducted in a group of 30 female players at the age of 9 and 10 years who were training in clubs in the Podlaskie Voivodeship. The subjects were divided into two groups according to the age category. The level of motor abilities and special effectiveness was assessed twice during the one-year training course in March and November, 2013. Results: In all trials we observed a statistically significant difference of mean results between the first and the second term of research in the group of girls aged 9 and 10. The correlation analysis of the results of attempts of motor abilities and the results of special efficiency assessed on the basis of the 100 ball Test showed that the statistically significant correlations exist. Conclusions: The statistically significant correlations between results of the 20-meter run, the simple reaction test and the results of the test assessing special fitness efficiency – the 100 ball Test – suggest that speed has an important impact on special fitness in tennis.