Temporal trends in weight-based disparities in physical fitness of children: 30-years of continuous surveillance through Slovenian national system

Abstract

Abstract Background Obesity in childhood has deleterious consequences for health while improving physical fitness can significantly reduce health risks related to high body mass index. This study leverages near-census data collected by the national fitness surveillance system in Slovenia to investigate the evolution of weight-based disparities in the physical fitness of 7–15-year-olds between 1989 and 2019. Methods We used annual data collected within the SLOfit monitoring system in the period between 1989–2019, totalling 4,256,930 participants (about 137 000 per year). We examined cardiorespiratory fitness (600-m run test), muscular fitness (60-s sit-ups, bent arm hang, and standing broad jump test) and skill-related fitness (backwards obstacle course, 60-m dash, arm plate tapping). We grouped children according to the IOTF cut-offs for BMI to those living with normal weight or excess weight and estimated changes in physical fitness over time by fitting quantile regression models separately by sex and age group, and then using segmented regression to identify the structure of trends over time. Results Weight-based disparities in physical fitness were large in 1989 and have further increased from 1989 to 2019 for all fitness components and across all age and sex groups. The increase in disparities was generally larger in boys than in girls, and 10–15-year-olds compared to younger children. Most of the increase in disparities in health-related fitness accumulated during the 2010s, when the fitness of children generally improved, but much less so in children living with excess weight. Conclusions Despite recent improvements in population fitness levels, children with excess weight seem to be left behind, which adds to existing health inequalities. Our results should encourage policymakers to redesign policies aimed at promoting physical activity and enhancing physical fitness to make them more equitable and ultimately lead to reducing inequalities in fitness.