Look at the picture above – it doesn’t look like that deadly, does it? Yet a growing body of research suggests that sitting down for long periods of time increases our risk of cardiovascular disease, type 2 diabetes, some cancers, and even increased risk of dementia. It's been said that sitting is the new smoking, but why, and what can we do about it?
Professor David Dunstan, a world authority on the role of sedentary behaviour in the development and management of chronic diseases, steps up to explain.
How much of the day does the average person in the West spend sitting?
The average Australian probably spends close to nine hours (this has also been shown in the US and Swedish populations) in sedentary time. That’s nine hours of muscular inactivity.
Why is it so bad for us -- what are the mechanisms involved?
This is yet to be fully understood, and is the subject of our own ongoing research. But sitting for long periods means you don’t contract your large skeletal muscles and this seems to have an impact on the body’s metabolism. And what we know from a physiological perspective is that contracting muscles assists the body in its regulatory processes, such as blood glucose uptake, to be used by the muscles for energy.
A correlation doesn’t always establish a cause, so how clear is it that sitting is causing all those diseases mentioned above?
It’s very difficult to clearly demonstrate this, as it would require a randomised controlled trial over many, many years. That said, the observational data of the link between too much sitting and those conditions is very consistent; several meta-analyses have confirmed this.
So what actually happens when we sit?
When we’re sitting our body is supported by the chair, and the big muscles of our lower limbs are inactive. We can use devices to measure the electrical activity when we sit, and it’s virtually a flat line. But the transition from sitting to standing leads to significant musculatory contraction; you have to do that to stop yourself from falling over, or to fight against the pull of gravity. Moving into walking enhances that contraction more, which is enhanced more again when you go into brisk walking, walk up stairs and/or jog.
The bottom line is that we have an absence of muscular activity for most of the day. The consequences are reduced efficiency of blood glucose uptake, and blood fat uptake. And we’re also starting to see blood pressure changes from being seated all day.
And contrary to popular belief, regular exercise won’t be enough to counter the ill effects of excessive sitting?
People often use the term sedentary to denote a person who doesn’t get enough exercise, but sedentary comes from the Latin verb, sedere, meaning ‘to sit’. We now know that even people who would be classified as “physically active” spend a huge amount of their time sitting. So when we talk about the hazards of too much sitting, it’s different from (and often in addition to) the hazards of too little exercise.
This puts a new perspective on the health paradigm in relation to exercise.
Yes, in that we should be thinking about a whole-of-day approach in relation to activity promotion. Not just encouraging people to do 30 minutes to an hour of moderate intensity exercise on most if not all days of the week, but thinking about the 16 hours in between.
Chairs have been around a long time; haven’t people always spent a lot of time on their backsides? Is this a new problem?
What we know is that we have become a more sitting-orientated society. Some folk in the media have referred to ‘sitaholics’. We sit down to eat breakfast, we sit when we’re commuting to work, when we’re at work, when we commuting home. We sit down to eat dinner, and then to watch television or spend time on the computer, and when we socialise with friends. As a society, we’re sitting down a lot more than we ever have in the past.
How seriously are these findings being taken in the workplace, and/or by health agencies?
While there is greater recognition of the issue in the community, the challenge is finding solutions to overcome it. Currently the furniture of the typical office environment only offers one choice; to sit down. Standing desks are getting some traction, but it’s not about standing or sitting, it’s about being able to move between standing and sitting. Some of the Scandinavian countries have had workstations where people can move between both for a number of years.
If office workers were provided with a workstation that allowed them to move between sitting and standing, would they actually use them? Old sitting habits die hard ...
I think they would, but they might need some support at first. We recently published the results of our Stand Up Victoria study, a 12-month randomized trial that involved more than 200 desk-based office workers, average age of 45. We assisted with the provision of organizational support, and ‘champions’ were recruited (usually the worksite team leader) to act as role models and promote the strategies. Everyone was given a dual-screen adjustable workstation, so they could move between sitting and standing, and coaching sessions on the appropriate postures for sitting and standing.
We used these coaching sessions to explain the intervention targets, encourage people to set their targets, identify barriers and how to overcome them. We also coached the participants on how to progressively increase the amount of time they spend standing throughout the day. Progression is the key here. It’s the same with exercise isn’t it? If you haven’t been doing much exercise you wouldn’t suddenly go out and do a two-hour run. You’d work your way up to it.
I imagine that the adjustable workstations would have had novelty value, but did it wear off? Did the participants go back to their chairs?
So our contact with workers was quite intensive for those three months, and then we left them to their own devices for the rest of the year. What we showed was that at the end of three months, compared to the control group, people were sitting on average 1.5 to two hours less per 8-hour day. But this was sustained after 12 months after they had been left with the workstation and to their own devices ... they were still sitting around 45 minutes less per eight-hour day than the control group. At the end of the intervention, nearly all of those who had workstations didn’t want to give them up.
Given most offices don’t provide adjustable workstations, do you have any alternative prescription on how to avoid the dangers of too much sitting?
That’s what we’re working on. We have to rapidly generate this evidence, because you’re not the first to ask. People ask us, ‘what should we reduce our sitting time to?’ but we don’t know that, or have that evidence yet. I don’t know if we ever will – we might only be able to provide a general message like we do for sun exposure, and it will invariably depend on the person.
Professor David Dunstan is Head of the Physical Activity laboratory at the Baker IDI Heart and Diabetes Institute in Melbourne and Professor at the Mary MacKillop Institute for Health Research, Australian Catholic University. You can read more about his campaign to “quit the sit” here.