Dose-response relationship between exercise and CVD risk factors : a meta-analysis of randomized controlled trials /

Abstract

Very strong scientific evidence shows that physically active people have better health, lower risk profiles for developing a number of disabling medical conditions, and lower rates of various chronic diseases than people who are inactive. However, due to the many variables associated with volume of physical activity and exercise, the dose-response relationship between exercise and cardiovascular disease (CVD) risk factors is not completely understood. The purpose of this investigation was to review and quantify the dose-response relationship between exercise and CVD risk factors using a meta-analytical review of randomized controlled trials. Studies that included adults and contained at least three CVD risk factor variables were identified using computer searches of the PubMed database restricting the search to randomized controlled trials studies published in English and for the period between January 1990 and December 2009. The search keywords were "exercise," "physical activity," "control," "cardiovascular," "CVD," "intervention," and "adults". Studies were classified in 12 possible categories based on the intensity and duration of exercise performed during the intervention. A total of 14 different variables representing CVD risk factors were investigated and the dose-response analysis was conducted for 12 of those variables. A total of 74 studies provided sufficient data to compute an Effect sizes (ES) expressed as Hedges adjusted g and were included in the analysis. VO2max had all positive ESs and a large positive effect. All other CVD risk factors had overall small effects. No significant differences were found among the ESs for different dose categories for any of the variables indicating the lack of a dose-response relationship. This study makes clear that CVD risk factors do not have the same response to exercise and the current recommendations for duration and intensity of exercise do not guarantee positive and effective results to all CVD risk factors. So