Is replacing sedentary time with bouts of physical activity associated with inflammatory biomarkers in children

This study aimed to investigate the theoretical impact of reallocating a specific amount of sedentary time with an equal amount of (a) total, and (b) ≥1min-bout-accumulated time spent in different activity intensities, on inflammatory biomarkers in 8-9 year old children. Accelerometry and inflammatory biomarker baseline data from the Transform-Us! Study (complete cases n=149) was utilized. Isotemporal linear models with Gaussian distribution and identity link functions were used to assess associations between the activity replacements and seven individual inflammatory biomarkers, including C-reactive protein (CRP), and Interleukin (IL)-2, 6, 8, and 10, as well as combined inflammatory and pro-inflammatory composite scores. Eighty-five percent of children met physical activity recommendations. Replacing 10 min of sedentary time per day with VPA, regardless of how this was accumulated, was beneficially associated with CRP and both combined composite scores. In contrast, replacing 10 min/day of sedentary time with ≥1-min MPA bouts was detrimentally associated with CRP and the inflammatory composite score. Substitutions with other activity intensities were not significantly associated with any individual inflammatory biomarkers, or combined inflammatory and pro-inflammatory composite scores. In healthy and active school-aged children, evidence of the theoretical impact of replacing sedentary time with physical activity, regardless of intensity or accumulation, on markers of systemic inflammation was limited. Longitudinal research is needed to investigate the long-term impacts of reallocating sedentary time with physical activity, and particularly VPA, for inflammatory biomarkers in children, including those with increased risk of inflammation.