The Effect of Exercise on the Cardiovascular Risk Factors Constituting the Metabolic Syndrome A Meta-Analysis of Controlled Trials

Background Numerous meta-analyses have investigated the effect of exercise in different populations and for single cardiovascular risk factors, but none have specifically focused on the metabolic syndrome (MetS) patients and the concomitant effect of exercise on all associated cardiovascular risk factors. Objective The aim of this article was to perform a systematic review with a meta-analysis of randomized and clinical controlled trials (RCTs, CTs) investigating the effect of exercise on cardiovascular risk factors in patients with the MetS. Methods RCTs and CTs >= 4 weeks investigating the effect of exercise in healthy adults with the MetS and published in a peer-reviewed journal up to November 2011 were included. Primary outcome measures were changes in waist circumference (WC), systolic and diastolic blood pressure, high-density lipoprotein cholesterol (HDL-C), triglycerides and fasting plasma glucose. Peak oxygen uptake ((V) over dotO(2peak)) was a secondary outcome. Random and fixed-effect models were used for analyses and data are reported as means and 95% confidence intervals (CIs). Results Seven trials were included, involving nine study groups and 206 participants (128 in exercise group and 78 in control group). Significant mean reductions in WC -3.4 (95% CI -4.9, -1.8) cm, blood pressure -7.1 (95% CI -9.03, -5.2)/-5.2 (95% CI -6.2, -4.1) mmHg and a significant mean increase in HDL-C +0.06 (95% CI +0.03, +0.09) mmol/L were observed after dynamic endurance training. Mean plasma glucose levels -0.31 (95% CI -0.64, 0.01; p = 0.06) mmol/L and triglycerides 0.05 (95% CI -0.20, 0.09; p = 0.47) mmol/L remained statistically unaltered. In addition, a significant mean improvement in (V) over dotO(2peak) of +5.9 (95% CI +3.03, +8.7) mL/kg/min or 19.3% was found. Conclusions Our results suggest that dynamic endurance training has a favourable effect on most of the cardiovascular risk factors associated with the MetS. However, in the search for training programmes that optimally improve total cardiovascular risk, further research is warranted, including studies on the effects of resistance training and combined resistance and endurance training.