Sedentary Physiology Part 3 – The Importance of Interruptions in Sedentary Time

Welcome to our 5-part series delving into the fascinating research being performed in the emerging field of sedentary physiology.  In Part 1 we discussed the basics of sedentary physiology, and in Part 2 we discussed the relationship between total sedentary time and negative health outcomes.  Today we look at the impact of breaks in sedentary time on health.

Yesterday we reviewed the evidence which links total sedentary time with increased risk of both morbidity and mortality.  But what about the manner in which you accumulate that sedentary time?  For example, does 7 hours of continuous sitting have the same impact as 7 hours of sitting interspersed throughout the day?  According to the evidence available so far – probably not.

A recent study by Genevieve Healy examined this issue in participants of the large Australian Diabetes, Obesity and Lifestyle (AusDiab) Study.  A total of 168 men and women aged 30-87 years were required to wear an accelerometer (an objective measure of bodily movement) during all waking hours for 7 consecutive days. Total sedentary time was measured as the number of minutes/day during which the accelerometer had a count of less than 100/min – a level of activity associated with reading or typing. A break in sedentary behavior was defined as any interruption of at least one minute during which the accelerometer count rose above 100 counts/min. This level of activity is typical of standing from a sitting position or walking a short distance (i.e. walking to the bathroom).

And what did the study find?

The greater the number of breaks taken from sedentary behavior, the lower the waist circumference, body mass index, as well as blood lipids and glucose tolerance. This was true even if the total amount of sedentary time and physical activity time were equal between individuals – the one who took breaks more frequently during their time at the office or while watching television was less obese and had better metabolic health. Importantly, the breaks taken by the individuals in this study were of a brief duration (<5 min) and a low intensity (such as walking to the washroom, or simply standing).

Unfortunately few other studies have been published in this area, but several interventions are currently underway in the USA and Australia, and I am very eager to see their results and post them here on the blog.  In the meantime, what are the practical implications of this epidemiological study?

While we should all be aiming to limit the time spent in sedentary behavior and increasing our time spent performing moderate-intensity physical activity, for many of us working in front of computers, countless hours of sedentary time are inevitable. However, according to this study, simply taking frequent short breaks from being lazy may have significant implications on our health. For example, while writing this post (total time of approximately 1 hour) I have counted myself getting up from the computer 3 times – some of these ‘breaks’ were a mere 30 second walk to the kitchen to get a drink. Thus, getting out of your chair at work once every hour to walk to the washroom, or to fill up your bottle of water, or to chat with a co-worker may be a good way to get your ‘breaks’ in. Similarly, while watching TV, why not get up and move around during the commercial break – by doing so you will give your body a break from doing nothing, which could have real health benefits.

As we’ve discussed so far this week, the available evidence suggests that both the total amount of sedentary time and the manner in which it accumulates are related to negative health outcomes, regardless of how physically active we are.  But what physiological mechanisms are at play, especially given that these relationships appear to be independent of physical activity?  For the answer(s), be sure to check back for Part 4 in our series tomorrow (now online here).

Travis & Peter

Healy, G., Dunstan, D., Salmon, J., Cerin, E., Shaw, J., Zimmet, P., & Owen, N. (2008). Breaks in Sedentary Time: Beneficial associations with metabolic risk Diabetes Care, 31 (4), 661-666 DOI: 10.2337/dc07-2046

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16 Responses to Sedentary Physiology Part 3 – The Importance of Interruptions in Sedentary Time

  1. DeLene says:

    Interesting! As a writer who works from home, I go through “feast” times when I’m super-busy with work and I have to chain myself to my desk for a month to get through it all. During these times, I make a point to do something at least 2 times a week (ride my road bike, yoga, race walk — down from my normal 5 times a week frequency), but I get mentally stressed out by my Distractibility Factor. Which basically means that I get distracted really easily and find myself getting up to check the mail, do wash, vacuum, clean the kitchen, pick up around the house, whatever. Guess I should look at these little breaks as an important health investment instead of a negative work habit.

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  2. Coturnix says:

    As you know, I am at the computer up to 15 hours a day. And I am skinny (pure genetics). But I get up very frequently – I would guess at least once per hour – and do something, like walk the dog, go for a walk around the block, whatever. Those are good “thinking” times as well, often composing blog posts in my head while I am offline on these brief breaks. These breaks also allow me to ‘cool off’ and decide not to respond angrily to some commenter on the blog which I would do if I just sat there all the time without interruptions.

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    • Travis Saunders, MSc, CEP says:

      I find that I also do some of my best thinking away from the computer, so I know exactly what you mean. It’s amazing how ideas seem to evaporate when I sit down in front of my laptop, only to have them flow out smoothly the second I walk to the water fountain.

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  4. FrauTech says:

    Okay I’ll be the voice of doubt again. I think this says more that fat people are less likely to take breaks. Not that if fat people take more breaks they would automatically lose weight or be less fat. I’d be interested in this study as a controlled group not an observational one. As in, if you force a group to take more breaks, and have a control group you’re forcing not to take any breaks, does your test group actually show health improvements over the control group.

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    • Travis Saunders, MSc, CEP says:

      That’s the million dollar question, and as we speak studies are being done using the exact protocol that you describe. Unfortunately the results aren’t out yet, so until then no one knows.

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  5. Carol says:

    I’m loving this series and looking forward to the next two posts. One change I’ll make now – as I watch TV in the evenings, I’ll be getting up during commericals far more often. During the day, although I am at the computer 65% of my time, I have a standing desk at work, which seems to meet the criteria described above.

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    • Travis Saunders, MSc, CEP says:

      That’s terrific – thanks for the note, Carol! How do you find working at a standing desk? I’ve heard it helps to still have a chair or stool so that you can sit from time to time, do you find that to be the case?

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      • Carol says:

        It does help to sit down once in a while. I use my chair when I am on the telephone, which is not all that often.

        The first week I had my standing desk, I was *really* tired. And I am in good shape (running 1/2 marathons, x-c skiing, etc.) I was surprised that I was tired that first week, but then the second week, it was no big deal. I also stand on a pad, which makes a huge difference in comfort too. I’ve been standing for about 6 months now and can’t imagine going back to a sitting desk.

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  7. Nora says:

    Seems like I’ve commented here about this previously; please forgive me if I repeat myself :)

    I have had a sit-stand desk and an exercise ball to sit on for about a year now. Before that I propped the keyboard on a box and stood up whenever I could. Whether standing or sitting I am usually listening to whatever kind of dance music I’m in the mood for (and I will dance to pretty much anything), so I can’t really sit perfectly still even if I want to. I get up and walk around, etc., as much as humanly possible. I walk/jog my two very energetic young dogs once or twice a day for 30 minutes or so, and my daily “commute” is about 1 kilometer each way on foot. I generally walk an additional kilometer or two or three during the day on my way around our large campus. I don’t spend a lot of time sitting in a car as I don’t drive. I do not have a television at home, or a computer. Unless I am in bed or napping on the couch, or sitting down to talk to someone who is unnerved by my pacing, I stand or dance or walk around (including to knit or play guitar or read).

    I have narcolepsy, so if I stop moving I fall asleep. If all this activity is making me thinner than I would be otherwise (and I think it is), then stopping would make me very fat. However the point of it (for me) is not to be thinner (although that would be awesome as I am not at all thin), but rather to stay awake with smaller doses of stimulant medications. Which have also failed to make me thin, btw.

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  9. While we should all be aiming to limit the time spent in sedentary behavior and increasing our time spent performing moderate-intensity physical activity, for many of us working in front of computers, countless hours of sedentary time are inevitable. However, according to this study, simply taking frequent short breaks from being lazy may have significant implications on our health.

    How is “working in front of computers” “being lazy”? (Won’t most people’s bosses think that the person taking a break to stroll around the office or walk over to the water cooler is the “lazy” one?) This phrasing is careless—even, I dare say, lazy!

    Also, I found this interesting and relevant. Dr. Sharma is on your blogroll, so you’ve probably seen it, but people reading this post might find it interesting. (Obviously, since the post came out after this series, it couldn’t be linked to when you were writing the series.)

    http://www.drsharma.ca/greater-attentional-cost-of-standing-with-obesity.html

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    • Travis says:

      Agreed – it was a poor choice of words. We’re trying to get away from moralistic terms like that in general, but sometimes they creep back in. Thanks for pointing it out.

      I did read Dr Sharma’s post on standing, and am still trying to figure out how this fits into the whole “sit less” paradigm (e.g. should we warn people that this may be an issue to watch out for when working in a standing position?). At the very least, it’s a reminder that putting these tips into practice is usually more complicated than it seems on the surface.

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