Does research support the claim that youth have become less active?
A recent report from WHO sparked new debate on the level of physical activity among children and youth. But what do the data actually say? Is there hold in the claim that young people are less active than previous generations?
Citing a 2019 report from the Norwegian University of Life Sciences (NMBU), the Norwegian website Utdanningsforskning.no write that today’s children and youth are less active than previously.
The NMBU researchers who wrote the report said they wanted to "counteract the trend of increasingly less physically active children."
And recently, Canadian researcher Mark Tremblay wrote in the research journal The Lancet Child and Adolescent Health:
"The electronic revolution has fundamentally transformed people's movement patterns by changing where and how they live, learn, work, play, and travel, progressively isolating them indoors (eg, houses, schools, workplaces, and vehicles), most often in chairs. People sleep less, sit more, walk less frequently, drive more regularly, and do less physical activity than they used to."
The study created headlines the world over, such as this one, in British newspaper The Guardian: More than 80% of adolescents not active enough, warns WHO. And this one, in Ugandan magazine The Independent: Young people’s health compromised by insufficient physical activity, new WHO report.
Equally inactive across the globe?
Only one in five young people are physically active at least one hour a day, the study concludes. This is based on data from 1.6 million students in 146 countries.
And the pattern is amazingly similar across time and place, according to the data. Youths in Norway, Turkey, China, Argentina, Uganda and the rest of the world's nations are about equally inactive. And they are about as inactive in 2001 as in 2016.
But there are several things that may seem paradoxical.
Could it be true that young people living in completely different environments and cultures actually share the same level of activity? And have there really been no major changes in the activity habits of youths between 2001 and 2016?
According to Statistics Norway, it was precisely during this period that everyone got access to the internet, smartphones and tablets.
If these new gadgets have totally changed our movement patterns, as Tremblay writes, why aren't these changes reflected in the measurements of young people's physical activity?
Little documentation for less activity
Professor Ulf Ekelund from the Norwegian School of Sport Sciences works with physical activity in young people, and is well acquainted with the international research in the field. He can explain some of these findings:
One issue is that physical activity surveys provide uncertain answers, and that there is very poor documentation as to whether the questions in studies can actually say anything about trends over time and differences between countries.
Another issue is that there is actually little evidence that young people are less active today.
Researchers have not been able to detect large drops in activity levels, not in questionnaire studies or studies with devices that record movement. In addition, we only have good data from devices like accelerometers, which measure actual movement, from the last 15 to 20 years.
We therefore have no idea of how physically active young people were in the 1960s, 1970s or 1980s.
Based on one question
“It’s important to know that the study was largely based on one question: How many days a week are you so active that you become breathless and sweaty for at least 60 minutes? The only individuals who are considered active enough are those who answer that they are this active seven days a week,” Ekelund says.
“I think when 15-year-olds answer this question, they interpret it as meaning that they do sports seven days a week. And it turns out that few adolescents actually do sports seven days a week,” he says.
In other words, this is probably a study that would define many people as not being active enough, Ekelund believes.
Some young people actually meet the recommendation for one hour of moderate to intense physical activity per day, but it may be that they walk a lot, but don’t train hard, for example.
“In addition we know nothing about whether or not the questionnaire can capture trends and changes over time,” says Ekelund.
“The main message is important: There are far too many people who are not sufficiently physically active. But based on this study, it is very difficult to make comparisons between different countries and over time,” he says.
Measured Norwegian young people with motion meters
To be able to make more precise comparisons of how much young people move, researchers need data from movement meters.
Ekelund and his colleagues at the Norwegian School of Sport Sciences have undertaken exactly these kinds measurements for Norwegian children and adolescents who were 6, 9 and 15 years old. The survey was conducted in 2005, 2011 and 2018. The researchers recently presented the results of the last round.
Interestingly, they show the same picture as the WHO survey:
“We see virtually no changes in physical activity,” Ekelund said
Around 90 per cent of six-year-olds and 70 per cent of nine-year-olds met the goal of an hour of moderate to hard activity per day in 2018. Corresponding figures among fifteen-year-olds were just under 50 per cent. Boys are consistently more active than girls.
For 9-year-old boys, there might be a slight decrease in activity, of about ten minutes a day, between 2005 and 2018, Ekelund said.
But otherwise there were little changes during the period.
This may indicate that the connection between computer use and physical activity is not as simple as one might think.
More time online
There is little doubt that technology plays a different role in the lives of today's young people than it did 20 years ago.
According to a report from the Norwegian Directorate for Children, Youth and Family Affairs, young people now spend an hour-and-a-half more on the internet every day, compared to 2006.
In one survey, almost half of 8th-grade girls stated that they spent most of the evening socializing on the Web or their mobile phones.
Over 20 per cent of the 8th grade boys said they spent most of the evening playing online games.
How, then, can it be that surveys say young people don’t seem to have become less physically active?
One does not exclude the other
Ekelund says the first answer to this is clear: it’s possible to spend a lot of time on the internet and social media, while also being physically active.
One activity does not exclude the other. The time the young people spend online may not be the time they would otherwise spend on being active. For example, the report from the Norwegian Directorate for Children, Youth and Family Affairs shows that young people today watch one hour less TV than youths in 2005.
It is also possible that youths’ activity has become polarized, Ekelund said.
Maybe youths who were active have become even more active, while inactive youths are becoming more sedentary? If so, the average would be about the same, although the level of activity at an individual level would have changed.
However, these are speculations. As of today, researchers have no evidence to suggest that new technology has led to less physical activity in the last 20 years.
But what about the period before 2000? Could there have been a major decline in physical activity in the decades before the turn of the millennium?
No good data from before
Ekelund says we just don’t know.
“We simply do not have any good data that make it possible to say how active young people were before. This also makes it impossible to compare today's youth with youths in the 1960s or 1980s,” Ekelund said.
Figures from organized sports show no sign that young people were more active before 2000. But when it comes to other leisure activities, we have very little information.
Some people may think back and remember more cycling, games of tag and football. But others may remember books, card games, listening to records or talking on the telephone. It’s impossible to draw any conclusions based on these kinds of memories.
In the end, all this ambiguity leaves more questions than answers.
One is why Tremblay, the Canadian researcher, says that technology causes young people to be less active than previously, in a comment on a study that doesn’t actually make the case that this is true.
In an email response to this question, Tremblay writes, "Your question is a common one, and one for which there isn’t the simple answer with a single reference that you can cite. But the circumstantial evidence is undeniable (to most, but not all)."
Tremblay writes that it is very difficult to measure physical activity, which means researchers need to rely on other data to determine if young people are less active than before.
Among these data are trends in obesity, physical fitness, lifestyle-related disesase, reported digital media use, trends in transportation and time spent indoor, and finally comparisons with cultures that can provide a glimpse of the past, like the Old Order Amish or Mennonite populations, and comparisons to countries at various stages of lifestyle transitions.
A lot of the data from such studies will suffer the same problems and uncertainties as studies of physical activity.
But Tremblay writes that “these data universally support the intuitive observation that adolescents today move less than those 70, 60, 50, 40, 30 years ago."
M. S. Tremblay, Challenges in global surveillance of physical activity, The Lancet Child & Adolescent Health, November 2019.
R. Guthold, G. A. Stevens, L. M. Riley, F. C. Bull, Global trends in insufficient physical activity among adolescents: a pooled analysis of 298 population-based surveys with 1·6 million participants, The Lancet Child & Adolescent Health, November 2019.