Reducing sedentary time or increasing moderate and vigorous intensity physical activity in youth? Associations with health outcomes

Abstract

Current recommendations for physical activity in young people state that those between 5 and 18 years of age should accumulate at least 60 minutes of moderate and vigorous intensity physical activity per day. Emerging evidence suggest that the majority of young people do not achieve the recommended levels of activity which may influence on their health. On the opposite end of the energy expenditure spectrum, sedentary time has been recognised as a potential risk factor for chronic disease in adults. Recent systematic reviews have suggested there is little evidence for a prospective association between baseline time spent sedentary and later health outcomes. There is a paucity of data examining the prospective associations between objectively measures physical activity and health outcomes. However, the cross-sectional evidence linking time in moderate and vigorous intensity physical activity with cardio-metabolic health outcomes is consistent with potentially greater magnitude of association for more vigorous intensity activity. Further, time spent sedentary appears unrelated to these outcomes following appropriate adjustments for time in moderate and vigorous intensity physical activity. The appropriate amount of time in moderate and vigorous intensity physical activity needed to prevent cardiovascular dysfunction in young people needs to be determined and the potential benefits of more vigorous intensity physical activity established. Additional large scale, well-designed prospective studies and randomised controlled trials are warranted to address these uncertainties.