More discussion of the definition for sedentary behaviour

Earlier this year more than 50 SBRN members signed a letter promoting an updated definition of the term “sedentary behaviour” (you can view that letter here).  That discussion has continued, as SBRN member Dr Ragnar Viir published (with  Alar Veraksitš) a comment on the new definition on the website of Applied Physiology, Nutrition, and Metabolism (available here).

Drs Viir and  Veraksitš write:

We welcome the proposal by Sedentary Behaviour Research Network (2012) to define standard terms whereby to describe our researches into the modern problem of excessive sitting. However, we have some concerns. Neither standing nor sitting can adequately be described just in terms of energy expenditure or neuromuscular activity. We must also include the seemingly subtle but measurable and significant effect of gravity on those muscles holding the body upright (Viir et al. 2007; Veraksitš et al. 2012).

Furthermore, if one defines “reclining” as lying down, then that is not “sedentary behaviour” at all; on the contrary, it has the crucial function of obtaining relief from the above effort, as we have shown (Viir et al. 2007; Veraksitš et al. 2012), and this has important application in rehabilitation (Viir et al.
2008).

For our research to be thorough it is important to be alert to the significant effect of gravity, subtle though it may be.

In response to this comment, Dr Mark Tremblay wrote:

I appreciate the concerns expressed by Drs. Viir and Veraksitš. They raise an important point regarding the effects of gravity on physiological functions while in different postures. Furthermore, nuances on how to define “reclining” are raised. The proposal by SBRN that sedentary behaviour be defined as any waking behaviour characterized by an energy expenditure ≤1.5 METs while in a sitting or reclining posture does not disregard the potential importance of gravity or other mechanical (e.g., pressure on tissues of contact points from sitting or type of clothing being worn) or environmental (e.g., indoor vs. outdoor) factors that may provoke, mediate, or moderate physiological or even cognitive functions. Nor does the definition preclude the study of sedentary behaviours such that perhaps a whole “family” of sedentary behaviour subcategories may emerge based on their physiological influence.

The fact that this discussion is occurring is evidence that our earlier letter is achieving its objective and that the mission of SBRN is being successfully pursued. Thanks and please keep the discussion going!

Both articles are available via the website of Applied Physiology, Nutrition and Metabolism.