Abstract: Objective: Electroencephalogram (EEG) mainly reflects the growth of the central nervous system which is the physiological basis of speed competence. The paper aims to study the development characteristics of adolescents’EEGwith their age increasing and the relationships between the characteristics and speed competence so as to find possible methods to predict speed through EEG characteristics. Methods: 620 students aged 6-16 in Sichuan, China were chosen to participate in the study. Their EEG when they were in quiet awaken state with their eyes closed was collected with Nation 9128W digital electroencephalograph for analysis of absolute and relative powerof each lead. Their 50-meterspeed was measured at the same time. Results: 1. The relative power of EEG presented significant difference in adolescents aged 6-16. With the increase in age, the relative power of δ wave, θ wave and α1 wave decreased, while the relative power of α2 and βwave increased. α2 wave sncreases rapidly during the period of 6-11 years old and 13-15 years old. 2. Males’ speed competence increase occurres during the period of 6-15 years old, while females’ during the period of 6-12; males’ sensitive period of speed is from 6 to 10 years old and from 12 to 14 years old, while females’ from 6 to 9 years old. 3. The correlation coefficient betweenα2% and 50-metre speed in high speed competence children is -0.64, and the correlation coefficientbetween 50 -metre speed and θ/βratio is 0.71.Conclusion: Children’s brain growthpresents obvious correlative features to age periods and has fast growth period. The best period for speed competence development occurres from 6 to 10 years old.The relative power of α2 wave andθ/βratio are an referential indicator for children’s speed competence development.

Key words: adolescents, electroencephalogram, speed, sensintive period, fitness