In September, Tremblay’s team at CHEO helped launch the Sedentary Behaviour Research Network (www.sedentarybehaviour.org) that has so far connected more than 100 researchers around the world.
Last week, he was finalizing a letter calling on scientific journals to use precise definitions in this burgeoning area of research.
Until recently, sedentary behaviour was just a “default term for the absence of physical activity,” Tremblay said.
One literature review found that definitions varied from less than 20 minutes a week of physical activity, to as much as 150 minutes. Few studies on sedentary behaviour reported the type (work, household, or leisure) or intensity of activity that was used to determine if someone was sedentary.
It makes a significant difference to our health.
“Two people could be training partners for a marathon and we run 45 minutes every day and in any survey we would be considered “active,” Tremblay said.
“But what if one of us lies there for the other 23 hours and 15 minutes and the other is a cashier who is on her feet all day?”
Both are technically meeting the requirements of Canada’s physical activity guidelines, which recommend adults be active for at least 2½ hours a week, he said. But the cashier is highly active while the other runner may have poor metabolic health.
The researchers signing Tremblay’s letter want “waking” sedentary behaviour defined as “an energy expenditure of less than or equal to 1.5 metabolic equivalents (METs) while in a sitting or reclining posture.” One METs is resting, while 1.5 METs might mean clicking a computer mouse while sitting, driving in a car, reading or doing homework.