Dr Grant Tomkinson from our Health and Use of Time Group made headlines when he presented to the American Heart Association Scientific Sessions in Dallas last November.
His research showing that the aerobic fitness of children worldwide has declined by about 15% since the mid-1970s was picked up by CBS, NBC and The Daily Mail, among others. The full paper has not yet been released, but you can read the conference abstract here.
We asked Grant a little more about the research, and the response.
You found yourself very much centre stage with this study. Did the media and public response surprise you?
Yes and no. Strategically, in the middle of the last year I tried to think of a different way in which my research can have impact. Typically we think in terms of journal publications and our citation count, but I wanted to try to get the research out to the average person in the best way possible. So I chose the biggest conference in our field, which is the American Heart Association conference, submitted an abstract, pitched it in a way that almost Americanised the wording, and road tested it in a way I hadn’t done before. And it worked.
So it didn’t surprise me because I wanted it to happen, but the degree to which it happened, yes that surprised me. The story ran in a two-week period in over 750 media outlets with over 400 million media impressions. So that was certainly beyond anything I thought. For three full days at the conference I was in the media centre and didn’t see a single presentation.
The idea that children are less fit is not hard to believe. Was it the magnitude of the problem that grabbed attention?
I think the question of children’s fitness had broad appeal and just about everyone – parents, kids, teachers, the general public – has an opinion. When we look at what had been written about the topic in the past, in both the lay and scholarly literature, there was much confusion and debate about whether there had been changes over time.
The fact that we could quantify it was important. When you can say the difference is about 15%, or 300 metres behind in a 1600 metre race, that’s something tangible that people can relate to. It gave them something to talk about and was almost a bit of a prop for parents – a little bit of one-upmanship over their kids.
How was the paper received at the conference itself?
I presented the paper in two ways, with very good response. The abstract itself was presented to a small audience of 20 to 30, but I was also invited to present it as part of a constellation of papers looking at the emergence of physical fitness as a primary health indicator. This was to 500 people, with the who’s who from the American Heart Association, local politicians, media and researchers. It was very well received.
Of course the pitch at the conference was very different to that for the media. The researchers were more interested in the science – how strong was the systematic review, how had we quantified the changes, and the key results.
Your study looked at cardiovascular endurance. Is this the key indicator of how fit children are?
Cardiovascular endurance – the fitness of your heart, lungs and blood vessels – is a strong and independent predictor in adults of cardiovascular disease now and into the future. There are other measures of fitness that are important as well, like muscular strength or muscular endurance, or how flexible you are. But none of those indicators are as important a predictor of your current or future fitness as cardiovascular endurance. Children tend to be fairly healthy anyway but cardiovascular endurance is a very good predictor of their cardiovascular disease risk, which tells us something about their probability of developing disease later on.
How did the research come about?
It was an extension of my PhD. In the late 1990s a few of us were talking about topical things that had not really been resolved – where there was debate in the literature – but also about the things that had been resolved – that we knew then that we hadn’t known 10 years before. It felt like the question of whether today’s children were fitter hadn’t really been resolved. Then you combine that with the fact that I come from an exercise science background, and that my wife had just delivered our first son. So I was interested in trying to see if there was in fact a decline in children’s fitness, and if so to try to come up with some strategies to turn the tide.
And how did you run it?
It was a systematic review process. We went out to try to find every single data set or study that had ever explicitly commented on changes in children’s physical fitness over time. There were very strict inclusion criteria, but we still came up with about 50 studies or serial national level data sets that looked at this story. That equates to over 25 million individual test results since the late 1950s.
Most came from high-income countries, with a sprinkling of middle income and only a few lower income. So it’s certainly biased in that respect, but the middle income and lower income countries show a similar trend. It’s just that we have less confidence in what has been happening in lower income countries because the studies are smaller and less in number.
It is interesting that the declines in endurance were similar across ages, genders and even regions.
There was not much difference between boys and girls or between age groups. The declines in fitness were a little greater in children aged 9-12 than in adolescents 13-17 but they weren’t substantial. The declines at the regional level were quite similar – when we compared Europe to North America to Asia to Africa – but at the national level they were very different.
This was particularly noticeable when you compared the big countries in Asia. In China and South Korea there were large declines, equivalent to 10% per decade since 1980, but in Japan there has been very little change since 1964. It’s a similar picture in Singapore.
How do you explain that?
There appear to be two main drivers to this decline in cardiovascular endurance. The first is that today’s children are fatter, and this affects performance in distance running, which we used to measure endurance. If you are carrying extra weight it is harder to perform the task.
The other is that children today are less exposed to long or repeated intensive physical activities. They tend to accumulate physical activity in shorter bursts – anaerobic, fast paced movements that are more intermittent in nature.
Some people have asked the question of whether it a genetic thing – are they different? No. Is it an environmental thing? I think it’s probably a constellation of social, environmental, physical and physiological factors that are driving it.
How do we, as a society, need to respond to these findings? Do we need to hit the panic button?
I don’t think so because in some countries there are suggestions the trend might be flattening out. Australia is one of those countries. We’ve got good evidence over the last few years – state level evidence, unfortunately we don’t have any national level evidence – suggesting that the cardiovascular endurance levels of children have stabilised and have maybe slightly improved. There is also some evidence of this in other countries – Spain and Japan. There is also evidence showing that the prevalence of overweight and obesity has stabilised in Australia since the mid 1990s. What we don’t know is whether this is temporary, or whether the ship has actually turned.
From an academic perspective, what is the next stage – the next piece in the puzzle?
The next step for us is to try to get fitness back on the national health agenda. We need to continue to work to get good quality data to drive policy. There have only ever been two national surveys of children’s fitness in Australia; the last was in 1985. And there has never been a national fitness survey of Australian adults.
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