As will be obvious to anyone on a bus or train or waiting for coffee, access to screen-based media has been revolutionised over the past two decades. In 2020, there were more than six billion smartphone users worldwide and almost global penetration. Yet, our understanding of how these devices have affected other behaviour, such as sedentary time, is limited.
In our study, recently published in the IJE, we used accelerometer measurements of sedentary time collected for the Norway-wide physical activity monitoring system to estimate that a 9-year-old boy or 15-year-old girl or boy spent, on average, 20 to 30 minutes more each day being sedentary in 2018 than in 2005. We also found that children and adolescents accumulate more of their sedentary time in longer uninterrupted periods, compared with a more fragmented pattern of activity in 2005. Children and adolescents now spend less time sitting for short periods of 5 minutes or less at a time.
We are all familiar with studies that investigate the associations between physical activity and outcomes such as death or cardiovascular disease. However, we rarely focus on the length of time over which these study participants are followed up to see if one of the outcomes occurs.
Over an average week, adults in the United
Kingdom living with chronic disease spend 61 minutes (9%) less on moderate
activity — such as gardening, brisk walking and housework — and 3 minutes (11%)
less on vigorous activity — such as running and aerobics — than their healthy peers.
Perhaps this comes as a surprise. After all, few of us would question the health benefits of keeping moving and getting our heart rate racing. Physical activity guidelines, such as those developed by the UK’s National Institute for Health and Clinical Excellence, specifically refer to the importance of increasing physical activity for chronic disease management.
So why have we observed a gap in activity
levels between those living with chronic disease and those without?
Findings from a community-based 5-year cluster randomised trial
Masamitsu Kamada, I-Min Lee and Ichiro Kawachi
Despite the well-known health benefits of physical activity, physical inactivity remains highly prevalent globally. Effective population strategies to promote physical activity are needed to reduce the global burden of non-communicable diseases stemming from physical inactivity. But the question is: how do we effectively promote physical activity at the population level, such as in entire communities?
Vicky Stiles, Brad Metcalf, Karen Knapp and Alex Rowlands
We don’t yet know whether it’s best to do it all at once, or little and often, but what we do know is that if a woman’s day-to-day activity contains 1–2 minutes of weight-bearing, high-intensity activity, similar to a medium-paced run for pre-menopausal women or a slow jog for post-menopausal women, she will have better bone health than women who do less. The benefits of high-impact activity on bone health are nothing new. What is novel about our findings is that better bone health is linked to such a short amount of daily activity, albeit at an intensity of the running variety.