Mediating effect of waist circumference on the relationship between physical activity and cardiorespiratory fitness in adolescents

Abstract

Background: Physical activity (PA) and waist circumference (WC) are both related to cardiorespiratory fitness (CRF). However, the extent to which PA relates to CRF through WC is not known. The purpose of this study was to examine the mediating effects of WC on the PA and CRF relationship in U.S. adolescents.Methods: Data from youths 12 to 15 years of age participating in the 2012 NHANES National Youth Fitness Survey (NNYFS) were used. Variables included self-reported moderate-to-vigorous PA (MVPA, min/day), WC (cm), and CRF (ml/kg/min). Linear regression was used to examine the sex-specific influence that MVPA and WC have on CRF while controlling for confounding variables. The multivariate delta method was used to estimate standard errors for the indirect effects. Results: Findings from the fully adjusted sex-specific models showed MVPA and WC independently and significantly (all p