Independent and Joint Associations of Cardiorespiratory Fitness and Muscle Fitness with Metabolic Syndrome in Korean Men

Background: Higher cardiorespiratory fitness (CRF) and muscle fitness (MF) attenuate metabolic syndrome prevalence in men. However, associations of CRF and MF with metabolic syndrome were poorly understood in South Korean men. Therefore, this study aimed to examine the independent and joint associations of CRF and MF on metabolic syndrome prevalence in Korean men. Methods: Korean men (n = 1,097, mean age = 44 years) were recruited from the central areas of South Korea for this Preventive Health Study (PHS) between May, 2007, and October, 2008, and they underwent a health examination, maximal treadmill test, and five different muscle fitness tests for this study. Results: From our data, separate age-and current smoking-adjusted logistic regression models revealed a graded inverse association of metabolic syndrome prevalence with CRF (P < 0.0001) and MF (P < 0.0001). The association of MF with metabolic syndrome remained significant and became attenuated with further adjustment, for CRF (P = 0.02). However, the association of CRF with metabolic syndrome remained unchanged when adjusted for MF (P < 0.0001). In the joint analysis using the low-strength and CRF unfit group as the baseline, the odds ratios (95% confidence intervals) for having metabolic syndrome were 0.52 (0.26-1.05) for the high-strength and CRF unfit group, 0.39 (0.24-0.65) for the low-strength and CRF fit group, and 0.28 (0.17-0.46) for the high-strength and CRF fit group. Conclusions: Both cardiorespiratory fitness and muscle fitness showed independent and joint inverse associations with metabolic syndrome prevalence in Korean adult men.