Greetings from Australia! Today is the first day of the International Congress on Physical Activity and Public Health in Sydney, Australia, and I’ve already seen more talks on sedentary behaviour than at any conference I have ever attended previously.
For me the day began with a pre-conference satellite session focusing specifically on sedentary behaviour. The presenters at the session will be familiar to regular readers of this site – Neville Owen, David Dunstan, and Genevieve Healy to name a few. The session began with a nice historical review of epidemiological research into the health impact of sedentary behaviour by Dr Wendy Brown. She pointed out that before 2005, most research using the word “sedentary” was referring to the lack of physical activity. Since 2005 however (and especially since 2009), there has been an exponential increase in the number of papers focusing specifically on the impact of sitting and other sedentary behaviours.
Next up was David Dunstan, who discussed his recent IDLE Breaks study, as well as his thoughts on the physiology of sedentary behaviour more generally. Interestingly, he argued quite strongly that bed rest and sitting should not necessarily be lumped together, since bed rest could be considered a far more “extreme” version of sedentariness than what humans experience on a regular basis. This differs from the approach that our group recently took in our our recent ystematic review of “acute” bouts of sedentary behaviour (which we defined as anything lasting 7 days or less). It’s a good point, and one that we struggled with when undertaking our review.
Unfortunately there is very little evidence directly comparing the physiological or behavioural impact of different types of sedentary behaviour, whether it is different postures (e.g. sitting vs lying down), or different contexts (e.g. tv viewing vs reading vs video games). In our review we found little difference between studies that imposed bed rest as compared to those that imposed sitting, although to be fair we only found a couple of studies looking at sitting, so it’s impossible to make any real generalizations for now (My own guess is that inactive muscle is inactive muscle, whether you’re sitting or lying down, although the smart money would probably bet on David’s best guess rather than mine)
Of interest, David also highlighted that we shouldn’t lump sleeping with sedentary behaviour, since sleep is meant to be restorative (and occurs largely in the fasting state), while daytime sedentary behaviour is generally performed in the post-prandial state (e.g. following a meal, when the body has to deal with elevated levels of glucose, insulin, etc). Which makes me think that a reduction in muscle’s ability to deal with circulating sugar or fat may not matter when a person is asleep, but could matter much more following a meal (especially one high in fat and/or sugar).
Charles Matthews then spoke about the measurement of sedentary behaviour, and urged researchers to include both energy expenditure and posture in their definition of sedentary behaviour, rather than focusing exclusively on energy expenditure. He also referred to the recent Sedentary Behaviour Research Network definition of sedentary behaviour, although he urged people to be careful not to let the focus on energy expenditure overwhelm the importance of taking posture into account.
Throughout the session there was discussion of the importance of changing our environment to make sitting less mandatory, and also of the difficulty of sitting less in the current environment. One interesting aspect of these talks on sedentary behaviour is that the audience gave a standing ovation following every talk as a way to stand up, thereby interrupting their sedentary time. I took the video below to show the interesting (some might say strange) effect this can give, although I like the fact that people are practicing what they preach.
On this same topic, Dr Stuart Biddle also made the point that it’s not necessary (or helpful) to demonize sitting – we all need to sit sometimes. The key is to just to sit a more reasonable amount.
Following this satellite session, we held a meeting of members of the Sedentary Behaviour Research Network, which attracted a good crowd for a discussion of the organization’s structure and function. For those who are members of the network, look for a survey that will soon be coming your way to more definitively plan how to move forward as an organization.
Finally, we then moved into the Opening Ceremony of the conference, followed by the first round of original presentations.
Tomorrow I’ll be giving my own talk at 2:05 pm in room 102, and hopefully doing some short interviews with other presenters that I can put up online. I’ll also try to change things up so that I’m not insulating myself in sessions focusing on sedentary behaviour for the whole conference. In the meantime, your loyal correspondent is enjoying the beautiful view from the balcony of the Sydney Convention Center.
If you’re interested in other news from the conference, you can follow the discussion on Twitter at #beactive2012 or over at beactiveblog.com. And if anyone comes across any great content on the conference (or is interested in creating their own), just let me know and I am happy to highlight it here on Obesity Panacea.
Enjoy the rest of Day 1!