Moderate-to-Vigorous Physical Activity From Ages 9 to 15 Years

TLDR

Reduced physical activity contributes to rising childhood obesity, yet few longitudinal studies have examined moderate‑to‑vigorous activity patterns in youth. The study aimed to characterize the patterns and determinants of moderate‑to‑vigorous physical activity among children aged 9 to 15 years. Using accelerometer‑derived MVPA data from 1,032 participants in the NICHD Study of Early Child Care and Youth Development, the authors performed longitudinal descriptive analyses at ages 9, 11, 12, and 15. MVPA fell from about 3 h/day at age 9 to 49 min on weekdays and 35 min on weekends by age 15, with a yearly decline of 38 min on weekdays and 41 min on weekends; boys remained more active than girls, yet both sexes showed similar decline rates, and girls fell below the 60‑min recommendation earlier (≈13 yr weekdays, 12.6 yr weekends) than boys (≈14.7 yr weekdays, 13.4 yr weekends).

Abstract

<h3>Context</h3>Decreased physical activity plays a critical role in the increase in childhood obesity. Although at least 60 minutes per day of moderate-to-vigorous physical activity (MVPA) is recommended, few longitudinal studies have determined the recent patterns of physical activity of youth.<h3>Objective</h3>To determine the patterns and determinants of MVPA of youth followed from ages 9 to 15 years.<h3>Design, Setting, and Participants</h3>Longitudinal descriptive analyses of the 1032 participants in the 1991-2007 National Institute of Child Health and Human Development Study of Early Child Care and Youth Development birth cohort from 10 study sites who had accelerometer-determined minutes of MVPA at ages 9 (year 2000), 11 (2002), 12 (2003), and 15 (2006) years. Participants included boys (517 [50.1%]) and girls (515 [49.9%]); 76.6% white (n = 791); and 24.5% (n = 231) lived in low-income families.<h3>Main Outcome Measure</h3>Mean MVPA minutes per day, determined by 4 to 7 days of monitored activity.<h3>Results</h3>At age 9 years, children engaged in MVPA approximately 3 hours per day on both weekends and weekdays. Weekday MVPA decreased by 38 minutes per year, while weekend MVPA decreased by 41 minutes per year. By age 15 years, adolescents were only engaging in MVPA for 49 minutes per weekday and 35 minutes per weekend day. Boys were more active than girls, spending 18 and 13 more minutes per day in MVPA on the weekdays and weekends, respectively. The rate of decrease in MVPA was the same for boys and girls. The estimated age at which girls crossed below the recommended 60 minutes of MVPA per day was approximately 13.1 years for weekday activity compared with boys at 14.7 years, and for weekend activity, girls crossed below the recommended 60 minutes of MVPA at 12.6 years compared with boys at 13.4 years.<h3>Conclusion</h3>In this study cohort, measured physical activity decreased significantly between ages 9 and 15 years.