How sitting might kill you

Maclean’s archives: Here’s science writer Kate Lunau with health news you won’t want to sit down for

Health news you won’t want to sit down for

Photograph by Jessica Darmanin

Shoehorning a visit to the gym into a busy day is difficult for almost anybody. Jacqueline Gradish, a personal trainer in Toronto, sees it all the time with her clients, who are “crammed into their workdays,” she says. “They come first thing in the morning, because it’s the only time they have control over.” Even after a session with Gradish, many will find themselves spending the rest of the day barely moving: seated at a desk, in a car, or after work, on the couch. “Some of them are literally tied to a screen,” she says.

Canadian adults are now spending about three-quarters of their time sedentary, according to Mark Tremblay, director of the Healthy Active Living and Obesity Research Group (HALO) at the CHEO Research Institute in Ottawa. A growing body of research suggests that too much sedentary time carries risks—even for those who diligently exercise. In September, Tremblay’s group launched the Sedentary Behaviour Research Network (SBRN) to study the impact of all the time we spend inactive, the dangers of which we’re only starting to understand. Jean-Philippe Chaput, junior research chair at HALO, puts it bluntly: “Independent of physical activity, sitting too much is killing us.”

According to Canadian guidelines, adults should do 150 minutes of moderate or vigorous aerobic physical activity per week, in 10-minute bouts or more. But only 15 per cent of us actually do that much, according to Statistics Canada; among that small group, many would qualify as “active couch potatoes,” who exercise for 30 minutes or so and spend the rest of their time relatively inactive. “A few [recent] studies have suggested that people who sit more die sooner, and have an increased risk of disease,” says Travis Saunders, a Ph.D. candidate at CHEO. “We’ve all been blind to it the past 30 or 40 years, focusing on the importance of physical activity. Sitting was just seen as a lack of activity,” not as an independent risk factor, as it’s now understood.

In one 2011 study in the European Heart Journal, researchers found that total sedentary time boosted levels of C-reactive protein, an inflammatory marker associated with a higher risk of many major diseases, including coronary heart disease. Another 2010 study looked at television watching habits among Australians, a useful stand-in for sedentary time. Watching just one extra hour of television per day was associated with an 11 per cent increased risk of all-cause mortality, and an 18 per cent increased risk of mortality from cardiovascular disease.

These results seem stark, but the study of sedentary behaviour is so new, there’s still no good definition of what it really means. “At the moment, it’s defined in very different ways,” Tremblay says. “Many people use it as a default category. If you haven’t met the guidelines [for exercise], you’re sedentary. But that’s not a measure of sedentariness, it’s a measure of exercise.” In a widely circulated letter, Tremblay and 51 other scientists called for a standard definition of sedentary behaviour: “any waking behaviour characterized by an energy expenditure [less than or equal to] 1.5 METs,” or metabolic equivalents, a measure of the energy demand of exercise, “while in a sitting or reclining posture.” (One MET is resting.) Someone who isn’t meeting physical activity guidelines should be classified as “inactive,” not “sedentary,” they say.

Saunders is partway through a new study on the short-term impact of sedentary behaviour on kids aged 10 to 14. They come into his lab on three separate days: arriving at 7:30 a.m. and leaving at 4:30 p.m., they’ll be fed a standardized breakfast and lunch, and then finally an all-you-can-eat buffet. In one session, they’ll be seated the entire day—playing video games, watching movies, doing homework—and even be wheeled to the bathroom. In another session, they’ll get a walk break every 20 minutes. “It’s not exercise, but it’s getting them up and moving,” Saunders says. And in a third, they’ll also run on a treadmill twice for 20 minutes at a time. (The three sessions are done in random order.) He expects to see hormonal and chemical changes within the body, like “higher insulin levels on the day when they sit all day, compared to when they have breaks or physical activity.”

As we begin to understand the impact of sedentary behaviour, some people are making changes. The Canadian Society for Exercise Physiology has released guidelines to cut back sedentary time for kids, suggesting they should limit “recreational screen time” to no more than two hours per day; guidelines for the early years and adults should follow. Gradish instructs her clients on exercises they can do while seated, like “squeezing their shoulder blades together to stimulate blood flow,” and counsels them to get away from their desks and take a short walk whenever they can. “I don’t recommend sitting on an exercise ball because you can still slouch,” she says, but she does suggest using yoga iPhone apps, which “get them off the couch for two minutes and into a stretch.” One of her clients got a dog to get outside more, she says; another rigged up a standing desk unit in his office so he isn’t constantly sitting down. The researchers who study sedentary behaviour practise what they preach: when contacted by Maclean’s, each conducted the interview while standing up.

The fact that sitting too much could be killing us—regardless of exercise—can sound discouraging to those who struggle to fit in gym time, but Tremblay insists it shouldn’t be. Regular exercise is tremendously important, he says: “All kinds of positive things will come from it, and almost everyone should do it.” Even so, sedentary time must also be reduced. “You can’t go for a 30-minute run in the morning and then chillax all day.” Cutting back sedentary behaviour can be as simple as biking to work instead of driving, doing some light chores in the evening, or even holding a “walking meeting” instead of a seated one, something he recommends.

“ ‘Let’s sit down and talk about it.’ We say that all the time, and we shouldn’t,” Tremblay says. “It’s hazardous to our health.”




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How sitting might kill you

  1. As an office worker, I’ve been thinking about this very issue of late.  I’m happy to see research into the hazards of the workworld we are creating – one where we are increasingly asked to be immobile for long periods at a time.

  2. Literally tied to a screen?

  3.  In the beginning of this article, they say “adults should do 150 minutes of moderate or vigorous aerobic physical activity per week, in 10-minute bouts or more.” So that’s a little more than 20 minutes per day. Then they say “You can’t go for a 30-minute run in the morning and then chillax all day.” Well, if you do it *every* day, that exceeds this previous recommendation. And it’s certainly more than “doing some light chores in the evening”, one of their final recommendations. Seems contradictory to me.

  4. As a full time office worker I do light exercise 2-3 hours a day + light walking for at least 15-20 mins after meals (lunch and dinner.. sometimes breakfast)

    Vigorous exercise is destroying your body… pushing your body to its limit, exhausting your energy and wearing away your cartilage.

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