Physical fitness and clustering of risk factors associated with the metabolic syndrome.Med. Sci. Sports Exerc.,Vol. 31, No. 2, pp. 287-293, 1999.Purpose:The purposes of this study were to 1) assess the prevalence of clustering of metabolic markers of the MS in a defined population and 2) determine the association between CRF and such clustering in a large group of adult men (N= 15,537) and women (N= 3,899).Methods:Metabolic markers of the MS included systolic blood pressure (BP) ≥ 140 mm Hg, serum triglycerides ≥ 150 mg·dL−1, fasting blood glucose ≥ 110 mg·dL−1, and elevated central adiposity (waist circumference > 100 cm). Cardiorespiratory fitness was defined as total time on a maximal treadmill exercise test. The cohort was grouped by the number of metabolic abnormalities and level of CRF. Associations between CRF and the number of metabolic abnormalities were assessed using proportional odds logit models.Results:Among men, the age-adjusted cumulative odds ratio for abnormal markers of the MS was 3.0 (95% C.I. 2.7-3.4;P< 0.001) for the least-fit men when compared with moderately-fit ones, and 10.1 (95% C.I. 9.1-11.2;P< 0.001) when compared with the most-fit men. Among women, the age-adjusted cumulative odds ratio was 2.7 (95% C.I. 2.1-3.5;P< 0.001) for the least-fit women when compared with moderately-fit ones, and 4.9 (95% C.I. 3.8-6.3;P< 0.001) when compared with the most-fit women.Conclusions:These cross-sectional results suggest that low CRF is associated with an increased clustering of the metabolic abnormalities associated with the MS in both adult men and women and support the need for future prospective analyses.