Today’s post comes from Rachel Colley (Senior Research Analyst in the Health Analysis Division at Statistics Canada), and describes a new paper released on April 18, 2018 looking at how time reallocations among sedentary behaviour, sleep, light-intensity movement and exercise are associated with health. The full article is available for free here. A brief summary of the article is also available here.
Exercise, adequate sleep and limited sedentary behaviour are all important health-promoting behaviours.1-3 Light-intensity movement is emerging as an independent predictor of improved cardiovascular health.4,5 The majority of the research linking these behaviours to health has looked at them in isolation, but interest has increased in examining these movement behaviours collectively.6,7
Our day is a fixed 24 hours that is generally made up of sleeping, sedentary behaviour, light-intensity movement, and exercise. By increasing time in any one of these types of behaviours, something else has to decrease. As highlighted by Rania Mekary and colleagues, “the benefits of different activities depend not only on the specific activity, but also on the activity it displaces.”8
Isotemporal substitution is a statistical technique that allows associations between increasing a given movement intensity and a health outcome to be estimated while considering the type of movement that is being replaced.
What did we do?
We used data from four cycles of the Canadian Health Measures Survey (n = 10,621). Sedentary time (SED), light physical activity (LPA) and moderate-to-vigorous physical activity (MVPA) were measured using Actical accelerometers while sleep duration, general health and mental health were self-reported. Obesity (body mass index and waist circumference) were directly measured. The isotemporal substitution technique was used to estimate the effect of substituting 30 minutes of one movement intensity for another, while controlling for total time and covariates. Mekary and colleagues do an excellent job of summarizing the technique here.
What did we find?
What did this article add?
The current Canadian physical activity guideline for adults recommends that adults should accumulate 150 minutes of moderate-to-vigorous intensity aerobic physical activity per week, in bouts of 10 minutes or more.8 This study confirms that MVPA is important for health but also suggests that some adults may benefit from messaging around the importance of simply reducing sedentary time and replacing it with light-intensity movement. This is in line with findings from the recently released 2018 Physical Activity Guidelines Advisory Committee Scientific Report9 which highlights the benefits of more modest doses and intensities of physical activity, particularly for individuals who are currently inactive.
About the Author:
Rachel Colley is a Senior Research Analyst in the Health Analysis Division at Statistics Canada. Her research is focused on examining the associations between physical activity, sedentary behaviour, and sleep on health in children, youth, and adults. Dr. Colley has been working with the accelerometer-measured physical activity data of the Canadian Health Measures Survey at Statistics Canada since 2007. Rachel can be reached at Rachel.Colley@Canada.ca.