Abstract: Purpose By investigating daily physical exercises of teenagers in downtown Chengdu and their behavior modes and by testing their physical fitness, this project aims to analyze the findings in order to provide data basis of formulating national adolescent physical activity recommendations. Methods 500 healthy teenagers from10 to17 are randomly choose and divided into 3 groups based on the information of ultrasonic bone-age piece and adolescent development scale the early stage group, the middle stage group and the late stage group. 50 (male and female)are randomly selected from each group(300 in total) to be the subject of a questionnaire investigation and physical fitness test. Results Teenagers who take more than 1 hour of physical exercise account for 43.43% in their early puberty, 45.65% in their medium puberty, and 19.36 percent in their late puberty, which shows that the time spent on physical exercises is decreasing with the age increasing; on the other hand, the test score of their power of gripping, jumping and bending improve with the increase of age. Conclusions The time of teenagers spent on daily physical exercises has reached the international standards in their early and medium puberty, but only 48.39 percent of teenagers in their late puberty meet the international standard. 20m shuttle run results can effectively evaluate the teenagers' aerobic capacity.

Key words: physical exercises, behavior modes, physical fitness, teenager