Abstract
Abstract *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, were calculated Δ1 (TP1 minus TP0), Δ2 (TP2 minus TP1), and Δ~total~ (TP2 minus TP0). *Results:* Changes in PAI were positively and independently associated with changes in ZPF in Δ1, Δ2, and Δ~total~. No significant associations of ΔST and ΔZPF were found. ΔBMI was negative associated with ΔZPF in Δtotal. Participants with higher fitness levels at baseline were those who showed positive changes in PAI over Δ~total~, decreased screen time and had the lowest increase in BMI over three years compared with those who were low-fit at baseline. Conclusions: Changes in PAI were the best predictor for changes in Fitness in children and adolescents in each year and over the three years of evaluation. BMI changes were associated with longitudinal changes in PF.
Highlights
Recent studies have been given increasingly interest to Physical Fitness (PF) by the recognition of its relationship with physical activity habits, health and welfare
This study aimed to examine the association of the changes in Physical Activity Index (PAI), sedentary time (ST) and Body Mass Index (BMI) with PF changes over three academic years and if there was some influence of fitness levels at baseline in those changes
Throughout the three years period, participants spent more time watching TV than using computer, with differences between TP0 and TP2, no significant differences were found for the whole screen time over the three time points
Summary
Recent studies have been given increasingly interest to Physical Fitness (PF) by the recognition of its relationship with physical activity habits, health and welfare. There is evidence from longitudinal studies that physical activity (PA) and PF have declined in the last decades [1,2,3] as a consequence of sedentary behaviours that characterize the free time entertainment of these new generations [4, 5]. PA has been promoted as a lifelong positive health behaviour in children and adolescents [26] and fitness has been proposed as a major marker of health status at any age [27]. This study aimed to examine the association of the changes in PAI, ST and BMI with PF changes over three academic years and if there was some influence of fitness levels at baseline in those changes
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