Children Sitting Too Long | Children's Health Blog

Date: 10/10/2015    Written by: Hiyaguha Cohen

Sitting Kids

Children Sitting Too Long | Children's Health Blog

We take public education for granted in the US, but it wasn't always so. Back in the 18th Century, plenty of people were violently opposed to the idea of sending kids to school, so much so, in fact, that they rose up in arms to resist compulsory education.1 Thomas Jefferson proposed legislation mandating public schools in both 1778 and 1780, but failed to get it through Congress. James Madison failed a few years later as well. In fact, it took nearly 20 years for a law to pass making public education mandatory.

What does this have to do with health today? It turns out that those Revolutionary Era parents might have been onto something, although not for the reasons they espoused. In those days, rich families didn't want their kids mixing with the riff raff in communal classrooms, and poor families didn't want their children yanked off the farms where they were needed to provide free labor.

It turns out that, from a health point of view, children might have been better off bailing hay and milking cows from dawn to dusk. A recent study has found that sitting for prolonged periods of time is very bad for young children, and as any adult reading this no doubt recalls, public education mostly involves sitting.2 The fact that sitting harms children shouldn't come as a surprise, really, since we already know that prolonged sitting by adults shortens lifespan, plus it can increase the risk of cancer, diabetes, obesity, cardiac problems, liver disease, and other dire health issues. But until the recent study, nobody worried over much about kids sitting in classrooms since kids, by definition, are more active than their parents--or at least they were in the past.

The new study, just published in the journal Experimental Physiology, discovered that young girls who sit for more than three hours at a stretch experience a severe decline in vascular function. In other words, sitting constricts the blood vessels in the girls' legs and prevents blood from  flowing in a healthy manner. When this happens, blood pressure rises and eventually, heart disease can result.

The research team, led by Ali McManus of the University of British Columbia, asked nine girls, aged nine to 12, to sit and play video games or watch television for three uninterrupted hours. A control group of girls also sat for the three hours, but each hour, they got up for 10 minutes and did a gentle ride on a stationary bike. The scientists measured vascular function at the start of the sitting marathon, and then again after. They found that after the three hours, vascular function declined by 33 percent—but not in the control group.

Then the girls switched groups the following day. Those who had been sitting without interruption were asked to do the intermittent exercise on the bicycles the second day, and the former exercisers were told to sit for the three hours. The results were the same: again, those girls who sat without interruption showed a marked decline in vascular function.

Dr. McManus gives insight on what those results mean. “For perspective,” she says, “in adults, a sustained one percent decline in vascular function has been shown to increase cardiovascular disease risk by 13 percent.” So if the girls experienced a 33 percent reduction in three hours and they sustained that reduction by constant sitting behavior, their risk of cardiovascular disease would increase by 429 percent.

On the other hand, it turned out that it didn’t take long for the blood vessels to bounce back to normal once the girls resumed normal activity. By the next day, their vascular function had returned to baseline, whereas studies on adults have shown that in older people the effects of sitting persist even after exercising. Kids, after all, do have better recovery than adults. The problem is that if kids sit day after day, month after month for the 12 years or so that they spend in school, plus the time they sit in front of screens (computer and TV) at home, they’re spending a lot of time in a state of compromised vascular function, even if  their blood vessels do bounce back. And as Dr. McManus points out, nobody knows the long-term effects of experiencing constant episodes of reduced vascular function. Then again, we do actually; by the time you become an adult, it’s deadly.

Critics can point to the fact that kids have been sitting in classrooms for a few hundred years, with little known ill effect. But in the not-so-distant past, daily physical education was mandated as part of the curriculum, at least in US schools, and that’s no longer the case. Plus, the old scenario of children playing ball on the street after school is largely a thing of the past. Instead, our kids sit at school all day and then play computer games after school while planted on the chair or couch--after sitting yet again while doing their homework. And apparently, they like it that way.

“I was surprised by how easy it was to get the girls to stay still for three uninterrupted hours,” Dr. McManus said. The kids happily stayed in place, playing with their devices or watching their screens. We are a lazy species from day one, perhaps.

Research reveals that the phenomenon of sedentary behavior among children is worldwide. One recent large-scale study that involved kids in 10 countries around the world, including Kenya, Brazil, Canada, Portugal, South Africa, China, the UK, Australia, and Columbia, found that kids on average sit for 8.5 hours daily.3 This represents more than half the waking hours for these children. Older children fare worse, at least in Canada, with those aged 12-19 sitting an average of 9.3 hours daily.4 Meanwhile, a British study of 300 kids starting at age five found a 30 percent drop in physical activity by the time the youth reached age 15, with the decline most pronounced among girls.5

Obviously, we’re not going to yank kids out of school so that they can work the farm. In fact, most adults now have sedentary jobs, and that’s most likely where our kids will end up; but it seems obvious that it would be in the best interests of health to incorporate a lot more physical activity into classrooms for young people of all ages—not to mention in the workplace for adults. When we talk about educational reform, this fact should be considered. Simply walking from one classroom to another down the hall when the bell rings isn’t enough. Children, by definition, need to move. Moving helps not only arterial function but also may make a dent in the ADHD epidemic.

And at home, parents need to encourage their children by setting a good example by exercising themselves and by providing ample opportunities for their children to engage in sports or other forms of activity beyond cruising the internet and watching videos.

  • 1. Brackemyre, Ted. "Education to the Masses." US History Scene 2 October 2015. (Accessed 5 Oct 2015.)
  • 2. Reynolds, Gretchen. “Sitting is Bad for Children, Too.” 23 September 2015. The New York Times. 2 October 2015.
  • 3. Katzmarzik, Peter et al. “Physical Activity, Sedentary Time, and Obesity in an International Sample of Children.” October 2015.  Medicine & Science in Sports & Exercise. 2 October 2015.,_Sedentary_Time,_and_Obesity_in.7.aspx
  • 4. “ParticipACTION Report Card for Children and Youth.” ParticipACTION. 4 October 2015.
  • 5. Metcalf, B.S., et al. “Exploring the Adolescent Fall in Physical Activity: A 10-Year Cohort Study.” October 2015. Med Sci Sports Exerc.

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