The combined influence of sedentary behavior and physical activity on cardiorespiratory fitness
PURPOSE: The aim of this study was to analyze the combined influence of objectively measured sedentary behavior and physical activity (PA) on cardiorespiratory fitness (CRF) in 2 506 Portuguese children and adolescents aged 10 to 18 years. METHODS: CRF was assessed with the Fitnessgram 20m shuttle-run test. PA and sedentary behaviour were assessed with accelerometry. Participants were classified as meeting current PA guidelines for youth vs not meeting; and as low vs High sedentary (according to the median value of sedentary time/day by age and gender); and then grouped as follows: Low Active - High Sedentary; Low Active - Low Sedentary; High Active - High Sedentary; High Active - Low Sedentary. Binary logistic regression models were constructed to verify the relationship between high CRF and the combined influence of PA/sedentary behavior, adjusting for age, gender and body mass index. RESULTS: Participants classified as high active/low sedentary (OR=1.849; 95%CI:1.246-2.744), as well as those classified as low active/low sedentary (OR=1.297; 95%CI:1.034-1.626) were more likely to be fit, compared with those from the low active/high sedentary group. CONCLUSIONS: These findings suggest that PA levels may not overcome the deleterious influence of high sedentary time. Our data stress the importance of promoting PA and discouraging sedentary behavior.