Does the association of habitual physical activity with the metabolic syndrome differ by level of cardiorespiratory fitness?

OBJECTIVE - Cardiovascular fitness (VO2max) and physical activity arc both related to risk of Metabolic disease. It is unclear, however, whether the metabolic effects of sedentary living are the same in fit and unfit individuals. The purpose of this study was, therefore, to describe the association between physical activity and the metabolic syndrome and to test whether fitness level modifies this relationship. RESEARCH DESIGN AND METHODS - physical activity Was measured objectively using individually calibrated heart rate against energy expenditure. VO2max was predicted front a submaximal exercise stress test. Fat mass and fat-free mass (FFM) were calculated using impedance biometry. A metabolic syndrome score was computed by summing the standardized values for obesity, hypertension, hyperglycemia, insulin resistance, hypertriglyceridemia, and the inverse level of HDL cholesterol and was expressed as a continuously distributed Outcome. To correct for exposure measurement cri-or, a random subsample (22% of cohort) re-attended for three repeat measurements in the year following the first assessment. RESULTS - The relationship of VO2max (ml O-2 (.) kg(FFM)(-1) (.) min(-1)) and the metabolic syndrome score was of borderline significance after adjusting for age, sex, physical activity, and measurement error (beta = -0.58, P = 0.06). The magnitude of the association between physical activity (kJ (.) d(-1) (.) kg(FFM)(-1)) and the metabolic syndrome was more than three tunes greater than for VO(2ma)x (standardized beta = - 1,83, P = 0.0042). VO2max however, modified the relationship between physical activity energy expenditure and metabolic syndrome (P = 0 036). CONCLUSIONS - This study demonstrates a Strong inverse association between physical activity and metabolic syndrome, an association that is much steeper in unfit individuals. Thus, prevention of metabolic disease may be most effective In the subset of unfit inactive people.