According to Statistics Canada, Canadian adults on average spend 9.6 hours a day sitting in 2020. As many people started to work from home since Covid, sedentary time could be even higher in 2021. If you live a sedentary lifestyle, you have a much higher chance of being overweight, developing type 2 diabetes or heart disease, and experiencing depression and anxiety (Betterhealth, n.d.).
Nowadays, our daily job makes us sit more than we move around. However, our body isn't designed for such a long time of sitting. The human body is built to move, and our unique body structure can strongly prove that. In our body, 360 joints and 700 skeletal muscles enable easy and free motion. Most of these joints have one possible path of movement or degree of freedom. For example, the shoulder and hip have upwards of three degrees of freedom（flexion/extension, internal/external rotation, adduction/ abduction). If we consider it from a mechanical perspective. The capacity that each of us has for differing movement types, patterns, and complexities is vast. However, most of the time, we sit more than our bodies need to. From 1991 to 2009, physical activities in the United States and China have declined 32% and 45% respectively (Ng & Popkin, n.d.). The substantial increase of sedentary behavior is the key factor leading to the decline of physical activity.
Now let's see what happens to your body when you sit down. As long as you sit down, the blood flow rate is dropped and venous return in your leg muscle is temporarily blocked. Meanwhile, the metabolism level decreased, and the number of calories burned plummeted from 128 to 62 calories per hour (Silver, 2021). Compared to standing, sitting will squeeze the chest capacity so that lungs have less space to expand when you breathe. Thus it limits blood flow rate and the amount of oxygen that fills the lungs and filters into the blood and blood flow rate. Our brain requires both of these things to remain alert, so your concentration level will most likely plummet as your brain activity slows (Dalkilinç, 2015).
Two hours later, HDL5 (High-density lipoprotein) , commonly known as “good” cholesterol (Mayo Clinic Stuff, 2020), is reduced by 20 percent in the blood (Gummelt, 2015). Another type of enzyme, Lipoprotein Lipase, which helps with weight loss, is temporarily inactivated (Dalkilinç, 2015). This Particular lipase is hidden in the walls of capillaries and is a type of special enzyme that reduces the amount of fat in the blood. Therefore, when you’re sitting, your body’s ability to break down fat is greatly reduced (Dalkilinç, 2015).
24 hours later, our body becomes less sensitive to insulin so that the insulin effectiveness drops 24 percent (Gummelt, 2015). This insulin resistance could further develop into type 2 diabetes (Felman, 2019). This long sedentary time is associated with the development of insulin resistance, dyslipidemia, increased blood pressure and impaired microvascular function (Hamburg et al., 2007, 2650-2656).
The long-term impact of sitting
As time passes by, the long-term health effects of sedentary sitting become severe. Professor Hidde P van der Ploeg, from the University Medical Centre in Amsterdam, followed 220,000 individuals 45 years or older for an average of 2.8 years. It has been discovered that all-caused mortality hazard ratios were 2%, 15% and 40% higher for 4 to less than 8, 8 to less than 11, and 11 or more hours of sitting respectively, compared with less than 4 hours of sitting (Ploeg et al., 2012, 494-500)。
If the study has been done even longer, like 12 years, the same pattern has been observed. Professor Rebecca Seguin, from Cornell University, followed 90,000 women ages 50 to 79 for an average of 12 years. It has been found that compared with less than 4 hours sitting a day, sitting more than 11 hours was associated with a 13%, 27% and 21% increase in Cardiovascular disease, coronary heart disease and cancer mortality respectively8.
In total, sedentary behaviour has a wide range of adverse effects on our body, including increased all-cause mortality, cardiovascular mortality, cancer rist, and metabolic disorders such as diabetes, hypertension, and dyslipidemia(Seguin et al., 2014, 122-135).
According to a report from the World health organization, sedentary lifestyle is one of the ten leading causes of death and disability in the world. Each year, around 6% of the mortality, which is around 2 million deaths, is directly associated with physical inactivity (World Health Organization, 2002).
Fortunately, the solution for this mounting threat is pretty simple and intuitive. If you get any choice to stand, then stand. If not, try to move around as much as you can. Since you have almost finished reading this article, why not stand up and stretch your legs right now? Take care of your body and it will pay back later.
1： Betterhealth. (n.d.). The dangers of sitting: why sitting is the new smoking. https://www.betterhealth.vic.gov.au/health/healthyliving/the-dangers-of-sitting.
2： Dalkilinç, M. (2015, March). Why sitting is bad for you. TED. Retrieved Aug 3, 2021, from https://www.ted.com/talks/murat_dalkilinc_why_sitting_is_bad_for_you/transcript?language=en#t-46029
3： Felman, A. (2019, March 26). What to know about insulin resistance. Medical News Today. https://www.medicalnewstoday.com/articles/305567
4： Gummelt, D. (2015, Feb 4). Proof that the human body was made to move. acefitness. Retrieved Aug 3, 2021, from https://www.acefitness.org/education-and-resources/professional/expert-articles/5282/proof-that-the-human-body-was-made-to-move/
5： Hamburg, N. M., McMackin, C. J., Huang, A. L., & Shenouda, S. M. (2007, Oct 11). Physical Inactivity Rapidly Induces Insulin Resistance and Microvascular Dysfunction in Healthy Volunteers. American Heart Association, 2650-2656.
6： Mayo Clinic Stuff. (2020, Nov 10). HDL cholesterol: How to boost your 'good' cholesterol. Mayoclinic. https://www.mayoclinic.org/diseases-conditions/high-blood-cholesterol/in-depth/hdl-cholesterol/art-20046388
7： Ng, S. W., & Popkin, B. M. (n.d.). Time use and physical activity: a shift away from movement across the globe. National Library of Medicine.
8： Ploeg, H. P. V. D., Chey, T., Korda, R. J., Banks, E., & Bauman, A. (2012). Sitting time and all-cause mortality risk in 222 497 Australian adults. Arch Intern Med, 494-500.
9： Seguin, R., Buchner, D. M., Liu, J., Allison, M., & Manini, T. (2014, Feb). Sedentary behavior and mortality in older women: the Women's Health Initiative. Am J Prev Med, 122-135.
10： Silver, N. (2021, June 1). Do You Really Burn More Calories While Standing? Healthline. https://www.healthline.com/health/fitness-exercise/calories-burned-standing
11： World Health Organization. (2002, April). SEDENTARY LIFESTYLE: A GLOBAL PUBLIC HEALTH PROBLEM. www.who.int. Retrieved Aug 3, 2021, from https://www.who.int/docstore/world-health-day/2002/fact_sheets4.en.pdf