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Q: CHILDREN’S LIFESTYLES ARE INCREASINGLY SEDENTARY. DOES THIS AFFECT THEIR OVERALL FITNESS?
A. Aerobic fitness levels among children and adolescents in the United States are decreasing, but this phenomenon is by no means unique to the United States: declining fitness levels in young people have been reported elsewhere.1
Researchers in Canada, for example, used accelerometers (devices that measure a subject’s change in speed over time) to evaluate the amount of time that Canadian children spend engaged in physical activity daily. They found that less than 10% of the children studied spent 60 minutes engaged in moderate-to-vigorous activity at least 6 days per week.1 Moderate-to-vigorous activity is defined by the Centers for Disease Control and Prevention (CDC) as activity that is six to seven times more intense than the state of rest for any given individual; this corresponds to brisk walking or jogging for most people.
A group of researchers in Australia evaluated peak oxygen consumption (VO2max, a standard measure of aerobic fitness) in 12- to 15-year-olds performing a shuttle-run test over a 5-year period. They found that there was a significant annual decline in performance among test subjects ranging from 0.4% to 0.8%.2 Similarly, scientists in Korea evaluated VO2max values in 6- to 18-year-olds performing 600- to 1,200-meter runs over the period from 1968 to 2000. These, researchers, too, reported annual declines in physical fitness ranging from 0.26% to 0.80% starting in 1984.3 Similar findings have been reported in Lithuania and the US, among others; it seems as if no country is immune to the development of declining physical fitness in children and adolescents.4–6
A decrease in aerobic fitness levels among children and adolescents is perhaps not surprising given our increasing reliance on technology. Today’s youth are spending less time than did their predecessors on obligatory physical activity, such as walking or bicycling to and from school.
Additionally, with increasing amounts of time spent performing sedentary activities, such as using the computer and watching television, less time is spent engaged in free play. As a result, organized sporting activities — gym class, recess, after-school sports teams — may represent the majority of physical activity that a growing child is likely to experience. The result is an overall decrease in children’s physical fitness.
- Colley RC, Garriguet D, Janssen I, et al. Physical activity of Canadian children and youth: accelerometer results from the 2007 to 2009 Canadian Health Measures Survey. Health Rep. 2011;22(1):15–23.
- Tomkinson GR, Olds TS, Gulbin J. Secular trends in physical performance of Australian children. Evidence from the Talent Search program. J Sports Med Phys Fitness. 2003;43(1):90–98.
- Tomkinson GR, Olds TS, Kang SJ, et al. Secular trends in the aerobic fitness test performance and body mass index of Korean children and adolescents (1968–2000). Int J Sports Med. 2007;28(4):314–320. doi:10.1055/s-2006-924357 [CrossRef]
- Volbekiene V, Griciute A. Health-related physical fitness among schoolchildren in Lithuania: a comparison from 1992 to 2002. Scand J Public Health. 2007;35(3):235–242. doi:10.1080/14034940601160649 [CrossRef]
- Kuntzleman CT, Reiff GG. The decline in American children’s fitness levels. Res Q Exerc Sport. 1992;63(2):107–111.
- Shephard RJ. Fitness of Canadian children: range from traditional Inuit to sedentary city dwellers, and assessment of secular changes. Med Sport Sci. 2007;50:91–103. doi:10.1159/000101354 [CrossRef]