There is no doubt that childhood and adolescence are decisive periods to acquire healthy lifestyle behaviors, like being physically active and participating in a variety of sports. When youngsters acquire an active lifestyle, there is a greater probability they will maintain it throughout their lives. The Active Healthy Kids Global Alliance released the Global Matrix 4.0 on Oct. 24, 2022, which compared indicators of physical activity in children and adolescents from 57 countries on six continents. Globally, overall physical activity received a grade of “D,” indicating that we are succeeding with less than half of children and adolescents (27-33%). Thus, there is an urgent need to address strategies to increase physical activity levels in children and youth.
In general, children are more active than adults, and physical activity levels decline substantially during childhood and adolescence. This decrease in physical activity starts at very early ages (i.e., from the age of 5 years). Although boys of all ages spend more time being physically active than girls, they tend to have a similar declining trend in their physical activity. While the observed reduction in average levels of physical activity during childhood appears to be universal across populations, there is a general lack of understanding of the correlates associated with the decline.
In our study, published in Medicine & Science in Sports & Exercise®, we described longitudinal trends in physical activity in childhood and explored putative individual-level (fitness, BMI, motor coordination) and environmental-level (family socioeconomic status, school characteristics) correlates of these trends. The study was conducted among primary school children in Portugal and involved repeated measurements of children recruited into one of six overlapping age cohorts who were each followed for three years. Time spent in moderate to vigorous physical activity was assessed using accelerometers, and children were instructed to wear the devices for seven consecutive days at each measurement period.
We found that both boys and girls experienced linear declines in moderate to vigorous physical activity with advancing age, and that boys were more active than girls at all ages. On average, boys engage in 17 more minutes of moderate to vigorous activity per day than girls. We also found that children who had higher musculoskeletal fitness or had a lower body mass index had a less steep decline in moderate to vigorous physical activity. However, contrary to our initial expectations, no significant link was found between family socioeconomic status and the physical activity decline. Yet, from the common environment (school characteristics), greater school playground dimensions predicted a steeper decline in physical activity.
The results of our study provide relevant information to be considered when designing and implementing strategies to attenuate declining levels of physical activity in childhood. We suggest that physical education and sports participation programs should emphasize the development of fundamental motor skills together with providing ample opportunities for fitness-enhancing physical activity. The finding that greater playground dimensions were associated with a steeper decline in physical activity is counterintuitive and requires further exploration. As with any observational study, it was impossible to control for the effects of unmeasured variables on the observed associations.
Sara Pereira earned a Ph.D. in sports sciences and specializes in sport, genetics and motor behavior. She is an assistant professor at Lusófona University in Lisboa, Portugal, and invited professor in the faculty of sport at the University of Porto in Porto, Portugal. Her research focuses on youth growth, motor development and lifestyle behaviors. She relies on a holistic interpretation of human development to best understand the intertwined relationships between individual and environmental characteristics that shape growth, motor development and lifestyle behaviors.
Peter T. Katzmarzyk, Ph.D., is professor and associate executive director for population and public health sciences at the Pennington Biomedical Research Center, where he holds the Marie Edana Corcoran Endowed Chair in Pediatric Obesity and Diabetes. His research program focuses on physical activity and obesity, with a special emphasis on pediatrics and ethnic health disparities. Dr. Katzmarzyk is an ACSM fellow, chair of the ACSM Evidence-based Practice Committee, member of the ACSM Board of Trustees and recipient of the ACSM Citation Award.
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