How too much sitting reduces your muscle mass
Kelsey Brown, BSc
May 23, 2023
Over the last few decades, the amount of time we spend sitting down has increased. When we are young, we often spend our free time sat watching TV or playing video games. As adults, many of us sit at a desk all day to work and then go home and sit down, watching TV to unwind. This could mean you are spending more than 7 hours being sedentary each day.
What is sedentary behaviour?
Sedentary behaviour is where we are seated, reclined or laid down whilst awake and have an energy expenditure of ≤1.5 metabolic equivalents (METs), in other words, times when we are not using a lot of energy or moving our muscles. METs are used to describe the amount of energy used per unit of time, for example, a brisk walk of 3-4 mph has a MET value of 5.
Sedentary behaviour doesn’t necessarily mean a lack of physical activity. It is widely recommended that adults participate in at least 75 minutes of vigorous-intensity or 150 minutes of moderate-intensity aerobic activity every week, with two days of strength-based exercise. Some research has found, however, that even those who partake in the recommended amount of physical activity can still be at risk of poor cardiometabolic health if they are sedentary for a large portion of their day.
One study, which investigated the levels of physical activity and sedentary behaviour in a multi-ethnic Asian population, discovered that almost half of the population (47.7%) were sedentary for 7 or more hours per day. Another recent study, which was conducted in 2020, found that Canadians on average spent more than half (68.9%) of their day being sedentary. If we assume they are getting 7 hours of sleep a night, these individuals are spending over 11 hours being sedentary. A large portion of our modern daily lives appears to be spent not using much energy, so what does this mean for our muscle health?
Sedentary behaviour and sarcopenia risk
Sarcopenia is the loss of muscle as you age, resulting in lower muscle mass, strength, and physical performance. Being sedentary for too long each day can speed up this muscle decline as you age, and the increase in daily sitting time that has become more prevalent in recent decades is thought to have a negative effect on muscle mass and function.
In a study which explored the relationship between sedentary behaviour, body composition, muscle function and sarcopenia in older adults, it was found that for every hour of additional sitting time, the risk of developing sarcopenia increased by 33%. One reason for this is that sedentary behaviour is associated with larger amounts of adipose tissue (body fat) and visceral adiposity (fat that is wrapped around your organs), which can result in a catabolic effect on your muscle, causing your muscle mass to decrease.
How to reduce this risk
One way to reduce the impact of sedentary behaviour is to incorporate more small bursts of activity into your day, allowing you to break up long periods of being sedentary. For example, try to go for a brief, 5-minute walk for every hour that you are working at your desk or sitting watching TV. If you work a 7-hour day, this will equate to a total of 35 active minutes, and will also reduce the negative impact of an extended block of sedentary behaviour.
You could also do small periods of bodyweight exercise throughout the day; instead of going for a walk, you could carry out some squats and push-ups for a 5-minute time period. As well as reducing your risk of sarcopenia, these simple resistance exercises would help to build your muscle mass/strength.
It is particularly important for older adults to ensure they aren’t spending too much time being sedentary, as they are at a higher risk of age-related muscle loss. Younger adults, however, should also be wary of spending too much time being sedentary, as they can also experience negative effects on their muscles and health, such as loss of muscle mass and increased risk of cardiovascular disease and type 2 diabetes. Implementing strategies to reduce sedentary time is therefore important for all individuals.
Bailey, D.P., Kilbride, C., Harper, J.H., Victor, C., Brierley, M.L., Hewson, D.J., & Chater A.M. (2023). The Frail-LESS (LEss Sitting and Sarcopenia in Frail older adults) intervention to improve sarcopenia and maintain independent living via reductions in prolonged sitting: a randomised controlled feasibility trial protocol. Pilot and Feasibility Studies. 9, (1), 1-12.
Gianoudis, J., Bailey, C.A., & Daly, R.M. (2014). Associations between sedentary behaviour and body composition, muscle function and sarcopenia in community-dwelling older adults. Osteoporosis International. 26, 571-579.
Hadgraft, N.T., Winkler, E., Climie, R.E., Grace, M.S., Romero, L., Owen, N., Dunstan, D., Healy, G., & Dempsey, P.C. (2021). Effects of sedentary behaviour interventions on biomarkers of cardiometabolic risk in adults: systematic review and meta-analyses. British Journal of Sports Medicine. 55, 144-154.
Katzmarzyk, P.T., Church, T.S., Craig, C.L., & Bouchard, C. (2009). Sitting time and mortality from all causes, cardiovascular disease, and cancer. Medicine & Science in Sports & Exercise.
Lau, J.H., Nair, A., Abdin, E., Kumarasan, R., Wang, P., Deviv F., Sum, C, F., Lee, E.S., Müller-Riemenschneider, F., & Subramaniam, M. (2021). Prevalence and patterns of physical activity, sedentary behaviour, and their association with health-related quality of life within a multi-ethnic Asian population. BMC Public Health. 21, 1939.
Mansoubi, M., Pearson, N., Clemes, S.A., Biddle, S.J.H., Bodicoat, D.H., Tolfrey, K., Edwardson, C.L., & Yates, T. (2015). Energy expenditure during common sitting and standing tasks: examining the 1.5 MET definition of sedentary behaviour. BMC Public Health. 15, 515.
Parry, S., & Straker, L. (2013). The contribution of office work to sedentary behaviour associated risk. BMC Public Health. 13, 296.
Prince, S.A., Roberts, K.C., Reed, J.L., Biswas, A., Colley, R.C., & Thompson, W. (2020). Daily physical activity and sedentary behaviour across occupational classifications. Health Reports. 31, (9), 13-26.
Smith, L., Tully, M., Jacob, L., Blackburn, N., Adlakha, D., Caserotti, P., Soysal, P., Veronese, N., Sánchez, G.F.L., Vancampfort, D., & Koyanagi, A. (2020). The Association Between Sedentary Behaviour and Sarcopenia Among Adults Aged ≥65 Years in Low- and Middle-Income Countries. International Journal of Environmental Research and Public Health. 17, 1708.
van der Ploeg, H., Hillsdon, M. (2017). Is sedentary behaviour just physical inactivity by another name? International Journal of Behavioural Nutrition and Physical Activity. 14, 142, 1-8.