Low muscle fitness is associated with metabolic risk in youth.

Abstract

To examine the independent associations of muscle fitness and cardiorespiratory fitness with clustered metabolic risk in youth. In 2005-2006, a cohort of 9- and 15-yr-olds (N = 2818) was randomly selected from all regions of Norway. The participation rate was 89% and 74% among the 9-and 15-yr-olds, respectively. We assessed muscular strength by measuring explosive, isometric, and endurance strength. Cardiorespiratory fitness was measured directly as peak oxygen uptake during a cycle ergometry test. Risk factors included in the composite risk factor score (sum of z-scores) were systolic blood pressure, triglyceride, high-density lipoprotein cholesterol, insulin resistance, and waist circumference. Muscle fitness was negatively associated with clustered metabolic risk, independent of cardiorespiratory fitness, and after adjustment for age, sex, and pubertal stage (beta = -0.112, P < 0.001). Independent of muscle fitness, an inverse association was found between cardiorespiratory fitness and clustered metabolic risk (beta = -0.337, P < 0.001). Moreover, the odds ratios for having clustered risk in the least fit quartile compared with the most fit quartile were 7.2 (95% confidence interval (CI)=4.3-12.0) and 17.3 (95% CI = 9.2-32.7) for muscle fitness and cardiorespiratory fitness, respectively. Our results show that muscle fitness and cardiorespiratory fitness are independently associated with metabolic risk in youth.