Nine-year-olds regularly engage in three hours of physical activity every day, but that drops off dramatically to below the recommended level of exercise when children hit their teen years, new research says.
Researchers in the U.S. have found that at ages nine through eleven, most American children meet the recommended guidelines of 60 minutes of moderate-to-vigorous exercise every day.
But only 31 per cent of 15-year-olds meet that target on week days, and only 17 per cent meet it on weekends.
The study was led by Dr. Philip R. Nader of the University of California San Diego. The findings are published in the July 16 issue of the Journal of the American Medical Association.
For their study, the researchers analyzed physical activity patterns among more than 1,000 children when they were nine, 11, 12 and 15 years of age. The kids wore an accelerometer, a monitor on a belt that measures movements by the minute, for one week of each year that they were studied.
The findings also showed that girls' levels of physical activity decreased at an earlier age than boys.
According to the study, girls went below the recommended one hour of daily activity on weekdays by an average age of 13.1, while boys didn't cross that threshold until an average age of 14.7.
The researchers said that if physical activity levels decline into the teen years, then they may continue to do so into adulthood.
"Consequently, there is a need for program and policy action as early as possible at the family, community, school, health care and governmental levels to address the problem of decreasing physical activity with increasing age," the authors wrote.
The study is released at a time when obesity rates in North America are on the rise. In fact, an estimated one-third of American children are overweight.
"Lack of physical activity in childhood raises the risk for obesity and its attendant health problems later in life," Dr. Duane Alexander, director of the National Institute of Health's Eunice Kennedy Shriver National Institute of Child Health and Human Development, said in a statement.
Research released last week recommended that more children be tested for cholesterol levels and that children as young as eight years of age be put on cholesterol medication if they need it.
The authors noted that further research is needed to determine why physical activity rates decline so rapidly as children enter their teen years. Of course, the fact that children spend more time in front of computers, televisions and video games is one theory.
However, the researchers also speculated that influencing factors include whether the kids are in an urban, suburban or rural environment; the proximity to safe places to play; and the quality of school gym classes.
But if the local school is cutting its physical education program or a family dwells in an apartment in a downtown neighbourhood, parents can still take some action to keep their kids moving.
"Whenever possible, parents could encourage family walks with their children," Nader said in a statement. "Even walking for as few as 15 minutes a day would provide health benefits."
Abstract:
Moderate-to-Vigorous Physical Activity from Ages 9 to 15 Years
Philip R. Nader, MD; Robert H. Bradley, PhD; Renate M. Houts, PhD; Susan L. McRitchie, MS; Marion O'Brien, PhD
Context: 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.
Objective: To determine the patterns and determinants of MVPA of youth followed from ages 9 to 15 years.
Design, Setting, and Participants: 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.
Main Outcome Measure: Mean MVPA minutes per day, determined by 4 to 7 days of monitored activity.
Results: 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.
Conclusion: In this study cohort, measured physical activity decreased significantly between ages 9 and 15 years.
