As a body of research grows studying sedentary time and sedentary behaviours, there is an increasing number of journals and scientific writings that are using a variety of definitions to describe terms like “sedentary behaviour” and “screen time”. This causes confusion, which makes it difficult to come to a scientific consensus about the exact physical consequences of sedentary behaviour.
After all, how can we know how harmful sedentary behaviour is if we’re not in agreement about what sedentary behaviour actually is? How can scientists recommend taking a “break” after a “bout” of sedentary activity, if we’re not sure what activities count as “sedentary,” which count as a “break,” and how long a “bout” is? For the sake of science, of the time and money it takes to practice scientific studies, and for all of our health, it is critical that we are all using the same language and engaging with the same understanding of words and their definitions. Otherwise, it’s like playing a sport and using two different scoring systems – nobody will ever know who won!
The importance of standardised terminology truly cannot be understated. Once standardised scientific terms are agreed upon in any field of study, it makes it easier for scientific studies to compare results with one another. This creates a climate of peer-reviewing that is impossible when one piece of literature uses the word “inactive” to mean what another study refers to as “stationary.” Standardised terminology makes it possible to compare, evaluate, and review data collected in various studies. It also makes it easy to communicate outcomes and results across platforms and different fields, from scientists to health care professionals to academics.
The Sedentary Behaviour Research Network
The Sedentary Behaviour Research Network (SBRN) convened to produce a terminology consensus project, where all parties agreed on the definitions of 10 movement-based terms. Though a global initiative is still needed, this is a hugely important first step towards producing standardised measurement protocols, consistent analytic procedures, and a globally agreed upon taxonomy.
The network first reviewed the wide variety of key terms used in sedentary behaviour research. They then took the information they gathered and proposed a list of terms and definitions through an online survey. Finally, 87 SBRN member participants responded to the survey and consensus definitions were finalised. Using the finalised definitions, they released a dictionary of standardised terminology which can hopefully become the industry standard in discussing standardised behaviours
Sedentary Behaviour, or Stationary Patterns?
Some of the discrepancies they discovered were minor, but others had a much larger potential for misunderstanding and spreading misinformation. For example, “sedentary behaviour” has had a variety of descriptions in different medical journals and literature. Most—but not all—sources described “sedentary behaviour” relative to MET expenditure. The Metabolic Equivalent of Task, or just metabolic equivalent, is a ratio measure of the energy expenditure of a particular physical activity, relative to a reference metabolic rate. Higher MET rates account for a greater energy expenditure, and lower MET rates describe lower energy expenditures. In other words, more intense physical activity has a higher MET, and sedentary behaviour has a lower MET.
What the scientific literature didn’t agree on, however, was what the appropriate MET measurement of a “sedentary behaviour” was. Some claimed that sedentary behaviour required 1.0-1.5 METs, others claimed less than 1.5 METs, while others claimed that sedentary behaviour required less than 2.0 METs.
The Results
In the end, the Sedentary Behaviour Research Network came up with standardised definitions for 9 behaviour patterns including physical inactivity, stationary behaviour, sedentary behaviour, standing, screen time, non-screen-based sedentary time, sitting all day, reclining, lying, and sedentary pattern behaviour.
While words like “lying” and “standing” might seem straightforward, the SBRN differentiated between “passive lying” such as on a couch, bed or floor, and “active lying,” which includes plank holds and other exercise positions, and uses more than the ≤ 1.5METs expended during passive lying. It also held that “active standing” such as on a ladder, while washing dishes, or even while juggling. Interestingly, passive standing included standing in line, while working an assembly line counts as active standing.
The results differentiated between physical behaviours of infants, toddlers, children, and adults, and gave examples and caveats of all terms as well as general standardised definitions.
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