| *_Objective:_* To analyze whether changes in Physical Activity Index (PAI), sedentary time (ST; TV and PC use), and Body Mass Index (BMI) made a significant contribution to longitudinal changes in Physical Fitness (PF) of children and adolescents. Additionally, we analyzed interaction between baseline fitness level and changes in fitness. 

*_Methods:_* This is a three years longitudinal study of 345 high school students aged 11-19 years. Students were invited to perform tests from Fitnessgram battery for strength (curl-ups, push-up), and Cardiorespiratory fitness (20m-shuttle run). PAI and ST were evaluated using a standard questionnaire. Standardized scores of physical fitness tests were summed (ZPF). Changes over time,... |
