Sitting is bad for you. Exercise is good for you. Sleep is too.
At present, we have 3 separate guidelines targeting these 3 separate behaviours. However, when combined these behaviours make up the full 24 hour period, so it seems a bit strange to separate them out into separate and distinct constructs, especially since they all interact and influence each other (e.g. more screen time means less sleep, more activity means more sleep, more sleep means more activity, etc). As a result, Canada is in the process of creating guidelines which integrate sleep, activity, and sedentary behaviour to give more holistic and less fractured advice to the public/policymakers/physicians/etc.
I’ve spent the past 3 days at a meeting learning about the development of these new guidelines, and I think they are a very interesting and relevant idea. Drs JP Chaput, Val Carson, Casey Gray and Mark Tremblay (full disclosure: friends and colleagues all) have recently released a commentary outlining the rationale for these new guidelines, which has been published in the International Journal of Environmental Research and Public Health. The article has an open access license, so I have included it in full below. It’s only a couple typed pages long, and worth the read.
I’m interested to hear what people think of this idea, as I think it represents a very different approach to thinking about activity/inactivity than has been employed in the past.
Human movement has been a necessity for survival throughout evolution. However, sitting has become the new norm in today’s environment despite the fact that we have not genetically adapted to this sedentary lifestyle (1). It is now common to refer to physical activity as having “health benefits”, even though the active state is the normal biological condition for metabolic processes (2,3). Lack of human movement should rather be perceived as “abnormal” and associated with numerous health risks (4,5).
Physical inactivity and childhood obesity represent pervasive, and arguably the greatest, health challenges to our children today (6,7). There is no easy solution to these serious public health threats and they need to be addressed by a range of strategies to maximize success. One of the strategies is to find ways to increase overall physical activity of children. However, health research has mainly focused on the impact of moderate-to-vigorous physical activity (MVPA), or even high-intensity physical activity, on various health outcomes. Although this approach has resulted in important contributions to the field, emerging evidence indicates that a broader, more inclusive and more integrated approach to understanding and promoting human movement is required to better address the current public health crisis of physical inactivity and childhood obesity.
There is no doubt that MVPA provides many important health benefits. However, MVPA only accounts for a small proportion (<5%) of the 24 hour day, even among active children and youth. In contrast, sleep (~40%), sedentary behavior (~40%) and LPA (~15%) make up approximately 95% of the day (Figure 1). Ignoring other components of the movement continuum while focusing efforts on MVPA limits our understanding of how habitual movement behaviors interact to impact children’s health. Indeed, recent efforts to address the single-minded focus on MVPA have led to a proliferation of sedentary behavior research and to the creation of the world’s first sedentary behavior guidelines for children and youth (8-10).
There is accumulating evidence that excessive sedentary behavior, particularly screen-based sedentary behavior (e.g. television viewing), has unfavorable effects on various health indicators, independent of MVPA (8,9). Likewise, short sleep duration is associated with many adverse health outcomes including obesity, type 2 diabetes, depression, suicidal ideation, and poor academic performance (11-14). This issue is of particular concern since a decrease in sleep duration has been observed over the past decades in children and adolescents (15,16). Finally, a growing body of evidence indicates that spending more waking hours in LPA compared to sedentary pursuits can provide health benefits (17-19). Reallocating sedentary time to LPA (e.g. TV watching to active play) is of substantial public health interest given that it is not feasible to participate in MVPA during all waking hours. Breaking up sedentary time with LPA is a more achievable and viable goal for increasing movement (i.e. number of steps per day) and acquiring associated health benefits than focusing solely on MVPA. However, current physical activity guidelines only focus on MVPA (and recently sedentary behavior) and do not take into consideration other important movement/non-movement behaviors that occur throughout the day. This issue is important because having one “unhealthy” movement behavior can moderate the health benefits of another. For example, the health benefits of MVPA can be mitigated if children have poor sleep habits and/or engage in excessive sedentary behavior (20). Conversely, increased physical activity could well decrease the detrimental effects of insufficient sleep and/or extended periods of sitting in some individuals (21,22).
Figure 1. Estimated distribution of movement behaviors over the 24 hour period.
2. Is there a need for 24 hour movement behavior guidelines?