Children’s Physical Activity Drops
From Age 9 to 15, NIH Study Indicates
By 15, Most Fail To Reach Recommended Activity Level
The activity level of a large group of American children dropped
sharply between age 9 and age 15, when most failed to reach the
daily recommended activity level, according to the latest findings
from a long-term study by the National Institutes of Health.
The analysis is one of the largest, most comprehensive of its
kind to date.
The researchers evaluated the children to determine whether they
achieved the minimum 60 minutes per day of moderate to vigorous
physical activity (MVPA) recommended for children.
At age 9, the children averaged roughly three hours of MVPA on
weekdays and weekends. By age 15, however, they averaged only 49
minutes per weekday, and 35 minutes per weekend.
"Lack of physical activity in childhood raises the risk
for obesity and its attendant health problems later in life," said
Duane Alexander, M.D., Director of NIH’s Eunice Kennedy Shriver National
Institute of Child Health and Human Development (NICHD). "Helping
American children maintain appropriate activity levels is a major
public health goal requiring immediate action."
The analysis was conducted on data collected for the NICHD Study
of Early Child Care and Youth Development, a long term study of
more than 1,000 children from ethnically and economically diverse
backgrounds. The study collected information on various other aspects
of children’s health and development. It was geared toward gathering
information on children's experience in various child care arrangements
but did not constitute a nationally representative sample of the
United States as a whole.
The analysis, appearing in the July 16 Journal of the American
Medical Association, was undertaken by Philip Nader, M.D.,
Emeritus Professor of Pediatrics at the University of California
San Diego, and other coauthors from the study.
Beginning at age 9, the researchers recorded the activity levels
of more than 800 children for four to seven days. The children’s
activity was recorded with an accelerometer, a device that records
movement, which the children wore on a belt. The researchers conducted
follow up tracking at ages 11, 12, and 15.
The 2005 Dietary Guidelines for Americans recommends that children
and adolescents engage in at least 60 minutes of physical activity
on most, preferably all, days of the week. (See http://www.health.gov/dietaryguidelines/dga2005/document/default.htm.)
As examples of moderate physical activity, the Centers for Disease
Control and Prevention list walking briskly, dancing, swimming,
or bicycling on level terrain. Vigorous physical activity includes
such activities as jogging, high-impact aerobic dancing, swimming
continuous laps, or bicycling uphill. Additional information is
available at http://www.cdc.gov/nccdphp/dnpa/physical/everyone/recommendations/children.htm
The researchers found that, at ages 9 and 11, more than 90 percent
of the children met the recommended level of 60 minutes or more
of MVPA each day. By age 15, however, only 31 percent met the recommended
level on weekdays, and 17 percent met the recommended level on
weekends. The researchers estimated that physical activity declined
by about 40 minutes per day each year until, by age 15, most failed
to reach the daily recommended activity level. On average, boys
were more active than girls, spending 18 more minutes per weekday
in MVPA than did girls, and 13 more minutes per day in MVPA on
weekends. The researchers estimated the age at which girls dropped
below the recommended level of 60 minutes of MVPA as 13.1 years
for weekdays, compared to boys, who dropped below the recommended
level at 14.7 years. For weekends, girls dropped below the recommended
level at 12.6 years, and boys at 13.4 years.
"This decline augurs poorly for levels of physical activity
in American adults and potentially for health over the life-course," the
study authors wrote. "Consequently, there is 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."
Dr. Nader explained that local school systems have a role to play,
by ensuring children receive periodic recess breaks and daily active
physical education. He added that local governments also could
strive to provide safe biking and walking routes around schools.
"But parents don’t need to wait for big changes" Dr.
Nader said. "Whenever possible, parents could encourage family
walks with their children. Even walking for as few as 15 minutes
a day would provide health benefits. On weekends, family outings
could be centered on longer walks or biking."
Increasing physical activity is a primary goal of We Can! (Ways
to Enhance Children's Activity and Nutrition), a science-based
national education program from the National Institutes of Health
to help children ages 8-13 maintain a healthy weight. We Can! provides
tips, evidence-based curricula and other resources for parents
and community programs to help children and their families make
better food choices, increase physical activity, and reduce recreational
screen time. More information is available at http://wecan.nhlbi.nih.gov or
toll-free at 866-35-WE CAN (866-359-3226).
The NICHD sponsors research on development, before and after birth;
maternal, child, and family health; reproductive biology and population
issues; and medical rehabilitation. For more information, visit
the Institute’s Web site at http://www.nichd.nih.gov/.
The National Institutes of Health (NIH) — The Nation's
Medical Research Agency — includes 27 Institutes and
Centers and is a component of the U.S. Department of Health and
Human Services. It is the primary federal agency for conducting
and supporting basic, clinical and translational medical research,
and it investigates the causes, treatments, and cures for both
common and rare diseases. For more information about NIH and
its programs, visit www.nih.gov.
Note: At the request of the institute, the second
sentence of the fourth paragraph was changed from the following to
the version posted above: "By age 15, however, they averaged
only 40 minutes per weekday, and 35 minutes per weekend." on
July, 16, 2008.