Sedentary Time and Its Implications on Our Health

By: Tana Mardian

Most of us spend a lot of time sitting down. Whether it’s attending class, watching TV, reading a book, or logging onto a Zoom call, the majority of our day to day activities largely consist of sitting in a chair. Since so much of our everyday lives revolve around sitting down, it’s important to look at the potential consequences of a sedentary lifestyle and what we can do about it.

For starters, we can look to The American College of Sports Medicine (ACSM) for advice on physical activity. The ACSM, in conjunction with the Center for Disease Control (CDC), has physical activity guidelines which advocate for at least 150 minutes of moderate activity per week, or 75 minutes of vigorous activity per week, in addition to muscle-strengthening exercises on 2 days of each week (ACSM). These guidelines suggest the weekly minimum amount of physical activity for an adult, meaning that there is a dose-response relationship between exercise and health benefits; there are further health benefits with exercising beyond the guidelines set forth by the ACSM. While these recommendations are helpful in getting the general population to engage in purposeful exercise, how do we address the continuous rise of sedentary lifestyles?

We must first consider the implications of sedentary time. A high amount of seated time is an independent risk factor for cardiovascular disease and may cause an increased vulnerability to dysfunction of vasculature in the legs (Restaino et al., 2016). Additionally, prolonged sedentary behavior has an association with increased risk of various chronic conditions, as well as mortality (Ekelund et al., 2016). Especially in adults that are at high risk of developing type II diabetes, there is a strong and adverse relationship between prolonged sedentary time and cardiometabolic health. Sedentary time might even be a stronger measure of poor health than moderate-to-vigorous physical activity for this group (Henson et al., 2012). So how can we attenuate the risks that are linked to sedentary behavior?

A meta-analysis by Ekelund et al. looked at 16 studies to assess how physical activity plays into the effects of prolonged sitting. From these studies, they were able to gather data on more than 1 million men and women. The article shows the hazard ratio associated with different amounts of sitting and TV-viewing time as they relate to different activity levels measured in MET hours/week (Figure 1). Their results indicate that about 60-75 minutes of moderate activity are necessary to eliminate the risk of mortality that is associated with high amounts of sitting time, but this level of activity will not eliminate the risk that is linked with prolonged TV-viewing time. For a lot of us, this amount of physical activity may not be achievable on a daily basis, so what can we do if we can’t dedicate an hour or more to exercise everyday?

There is evidence to suggest that breaks in sedentary time could help with the risks associated with prolonged sitting. A study on Australian adults without diabetes looked at the relationship between breaks in sedentary time and adiposity, lipids, blood pressure, and glucose. Independent of the amount of sedentary time, time spent doing moderate-to-vigorous exercise, and average intensity of the breaks, interruptions in sedentary time were advantageously linked to waist circumference, BMI, triglyceride levels, and 2-hour plasma glucose. These breaks were measured by an accelerometer, in which the participants likely stood up and walked around for more than one minute (Healy et al., 2008). Another review points out that these light, ambulatory breaks might be adequate in improving metabolic markers for those that are physically inactive or have type II diabetes, but a higher intensity or amount might be necessary for younger, physically active individuals (Benatti & Ried-Larsen, 2015). Another study investigated the effects of a 5 minute micro-bout of activity vs. a single 45 minute physical activity bout on sedentary time in overweight/obese adults. Both treatment interventions showed increases in physical activity, energy expenditure, as well as feelings of vigor, and insulin sensitivity improved (De Jong et al., 2018). 

All of this evidence has important implications on physical activity guidelines as our lifestyles become more and more sedentary. Given that these short and light intensity breaks improved metabolic markers and feelings of vigor while also decreasing feelings of fatigue, something as simple as getting up during commercial breaks or taking a short walk around the office could have beneficial effects on health. So, while over an hour of moderate intensity physical activity may be needed to mitigate  the risks associated with sitting at our desks all day, there are certainly small things we can do in our everyday life that could have big impacts on our health.

Figure 1. 

Meta-analyses of the relationships of sitting time and MET hours of physical activity with all-cause mortality (A) and of time spent viewing TV and MET hours of physical activity with all-cause mortality (B)

From “Does Physical Activity Attenuate, or even eliminate, the detrimental association of sitting time with mortality? A harmonised meta-analysis of data from more than 1 million men and women,” by U. Ekelund et al., 2016, The Lancet, 388(10051), p. 1307. Copyright 2016 by Elsevier.

Reference List:

American College of Sports Medicine, Riebe, D., Ehrman, J. K., Liguori, G., & Magal, M. (2018). ACSM’s guidelines for exercise testing and prescription (Tenth edition.). Philadelphia: Wolters Kluwer.

Benatti, F. B., & Ried-Larsen, M. (2015). The effects of breaking up prolonged sitting time. Medicine & Science in Sports & Exercise, 47(10), 2053–2061. https://doi.org/10.1249/mss.0000000000000654 

De Jong, N., Debache, I., Pan, Z., Garnotel, M., Lyden, K., Sueur, C., Simon, C., Bessesen, D., & Bergouignan, A. (2018). Breaking up sedentary time in overweight/obese adults on work days and non-work days: Results from a feasibility study. International Journal of Environmental Research and Public Health, 15(11), 2566. https://doi.org/10.3390/ijerph15112566 

Ekelund, U., Steene-Johannessen, J., Brown, W. J., Fagerland, M. W., Owen, N., Powell, K. E., Bauman, A., & Lee, I.-M. (2016). Does physical activity attenuate, or even eliminate, the Detrimental Association of sitting time with mortality? A harmonised meta-analysis of data from more than 1 million men and women. The Lancet, 388(10051), 1302–1310. https://doi.org/10.1016/s0140-6736(16)30370-1 

Healy, G. N., Dunstan, D. W., Salmon, J., Cerin, E., Shaw, J. E., Zimmet, P. Z., & Owen, N. (2008). Breaks in sedentary time: Beneficial associations with Metabolic Risk. Diabetes Care, 31(4), 661–666. https://doi.org/10.2337/dc07-2046 

Henson, J., Yates, T., Biddle, S. J., Edwardson, C. L., Khunti, K., Wilmot, E. G., Gray, L. J., Gorely, T., Nimmo, M. A., & Davies, M. J. (2013). Associations of objectively measured sedentary behaviour and physical activity with markers of Cardiometabolic Health. Diabetologia, 56(5), 1012–1020. https://doi.org/10.1007/s00125-013-2845-9 

Restaino, R. M., Holwerda, S. W., Credeur, D. P., Fadel, P. J., & Padilla, J. (2015). Impact of prolonged sitting on lower and upper limb micro- and macrovascular dilator function. Experimental Physiology, 100(7), 829–838. https://doi.org/10.1113/ep085238

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